[ML][inference] AI Connector: allows user to manually set context length window (elastic#230005)

## Summary

Part of elastic#228716

Because we're mutating the GenAI connector schemas by introducing a new
field, the change needed to be done in two different serverless
releases.

elastic#228371 introduces the model
changes for the connector schemas
This PR adds the ability to set the `contextWindowLength` config
property in the UI for the AI/Inference connector.
This PR must be merged after
elastic#228371 is deployed in production.

The input field will only show up for providers with the
'chat_completion' supported task type.

<img width="999" height="1273" alt="image"
src="https://github.com/user-attachments/assets/1c7aa343-523e-48d5-9f4b-63c194f4b262"
/>

Enforces chat_completion task type when setting contextWindowLength:

<img width="645" height="938" alt="image"
src="https://github.com/user-attachments/assets/2df17065-95ae-4217-842f-a0e360a78b73"
/>

<img width="932" height="1190" alt="image"
src="https://github.com/user-attachments/assets/eb694a47-5f94-4689-8cff-8dc1c4880433"
/>



### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This was checked for breaking HTTP API changes, and any breaking
changes have been approved by the breaking-change committee. The
`release_note:breaking` label should be applied in these situations.
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [ ] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.


Describe the risk, its severity, and mitigation for each identified
risk. Invite stakeholders and evaluate how to proceed before merging.

- [ ] [See some risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx)
- [ ] ...

---------

Co-authored-by: Elastic Machine <[email protected]>

Author: 2 people

x-pack/platform/packages/shared/kbn-inference-endpoint-ui-common/src/components/additional_options_fields.test.tsx

@@ -0,0 +1,225 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import React from 'react';
+import { AdditionalOptionsFields } from './additional_options_fields';
+import { render, screen } from '@testing-library/react';
+import { I18nProvider } from '@kbn/i18n-react';
+import { Form, useForm } from '@kbn/es-ui-shared-plugin/static/forms/hook_form_lib';
+import type { Config } from '../types/types';
+import { CHAT_COMPLETION_TASK_TYPE } from '../constants';
+
+const MockFormProvider = ({ children }: { children: React.ReactElement }) => {
+  const { form } = useForm();
+
+  return (
+    <I18nProvider>
+      <Form form={form}>{children}</Form>
+    </I18nProvider>
+  );
+};
+
+const textEmbeddingTask = 'text_embedding';
+
+const mockConfig = {
+  provider: 'openai',
+  contextWindowLength: '',
+  inferenceId: 'testId',
+  providerConfig: {},
+  taskType: CHAT_COMPLETION_TASK_TYPE,
+} as unknown as Config;
+const taskTypeOptions = [
+  { id: textEmbeddingTask, label: textEmbeddingTask, value: textEmbeddingTask },
+  {
+    id: CHAT_COMPLETION_TASK_TYPE,
+    label: CHAT_COMPLETION_TASK_TYPE,
+    value: CHAT_COMPLETION_TASK_TYPE,
+  },
+];
+
+describe('AdditionalOptionsFields', () => {
+  describe('contextWindowLength', () => {
+    it('should render contextWindowLength field when task type options include chat_completion', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={true}
+            selectedTaskType={CHAT_COMPLETION_TASK_TYPE}
+          />
+        </MockFormProvider>
+      );
+
+      const inputField = screen.getByTestId('configuration-formrow-contextWindowLength');
+      const inputLabel = screen.getByTestId('context-window-length-details-label');
+      const isInputInvalid = inputField.getAttribute('aria-invalid');
+      expect(inputField).toBeInTheDocument();
+      expect(inputLabel).toBeInTheDocument();
+      expect(isInputInvalid).toBeNull();
+    });
+
+    it('should render contextWindowLength field as valid when selectedTaskType is chat_completion', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={{
+              ...mockConfig,
+              taskType: CHAT_COMPLETION_TASK_TYPE,
+              contextWindowLength: 500,
+            }}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={true}
+            selectedTaskType={CHAT_COMPLETION_TASK_TYPE}
+          />
+        </MockFormProvider>
+      );
+
+      const inputLabel = screen.getByTestId('context-window-length-details-label');
+      const inputField = screen.getByTestId('configuration-formrow-contextWindowLength');
+      const isInputInvalid = inputField.getAttribute('aria-invalid');
+      const inputNumberField = screen.getByTestId('contextWindowLengthNumber');
+      const inputValue = inputNumberField.getAttribute('value');
+      expect(inputLabel).toBeInTheDocument();
+      expect(isInputInvalid).toBeNull();
+      expect(inputNumberField).toBeInTheDocument();
+      expect(inputValue).toBe('500');
+    });
+
+    it('should render contextWindowLength field with invalid indicator when selectedTaskType is not chat_completion', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={{ ...mockConfig, taskType: textEmbeddingTask, contextWindowLength: 500 }}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={true}
+            selectedTaskType={textEmbeddingTask}
+          />
+        </MockFormProvider>
+      );
+
+      const inputField = screen.getByTestId('contextWindowLengthNumber');
+      const isInvalid = inputField.getAttribute('aria-invalid');
+      expect(isInvalid).toBe('true');
+    });
+
+    it('should hide contextWindowLength field when chat_completion is not a task option', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={[]}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={true}
+            selectedTaskType={textEmbeddingTask}
+          />
+        </MockFormProvider>
+      );
+
+      const inputField = screen.queryByTestId('configuration-formrow-contextWindowLength');
+      const inputLabel = screen.queryByTestId('context-window-length-details-label');
+      expect(inputField).not.toBeInTheDocument();
+      expect(inputLabel).not.toBeInTheDocument();
+    });
+
+    it('should hide contextWindowLength field when allowContextWindowLength is false', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={false}
+            selectedTaskType={textEmbeddingTask}
+          />
+        </MockFormProvider>
+      );
+
+      const inputField = screen.queryByTestId('configuration-formrow-contextWindowLength');
+      const inputLabel = screen.queryByTestId('context-window-length-details-label');
+      expect(inputField).not.toBeInTheDocument();
+      expect(inputLabel).not.toBeInTheDocument();
+    });
+  });
+
+  describe('taskTypeOptions', () => {
+    it('should render taskTypeOptions section', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={false}
+          />
+        </MockFormProvider>
+      );
+
+      const taskTypeTitle = screen.getByTestId('task-type-details-label');
+      const taskTypeButtons = screen.getByTestId('taskTypeSelect');
+      expect(taskTypeTitle).toBeInTheDocument();
+      expect(taskTypeButtons).toBeInTheDocument();
+
+      taskTypeOptions.forEach(({ id }) => {
+        const optionButton = screen.getByTestId(id);
+        expect(optionButton).toBeInTheDocument();
+      });
+    });
+
+    it('should have single task type selection when only one task type option', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={[taskTypeOptions[0]]}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={false}
+          />
+        </MockFormProvider>
+      );
+      const taskTypeButton = screen.getByTestId('taskTypeSelectSingle');
+      expect(taskTypeButton).toBeInTheDocument();
+    });
+
+    it('should disable task type selection on edit', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={false}
+            isEdit={true}
+          />
+        </MockFormProvider>
+      );
+      const taskTypeButtonDisabled = screen.getByTestId('taskTypeSelectDisabled');
+      expect(taskTypeButtonDisabled).toBeInTheDocument();
+    });
+  });
+
+  describe('inferenceId', () => {
+    it('should render the inferenceId section', () => {
+      render(
+        <MockFormProvider>
+          <AdditionalOptionsFields
+            config={mockConfig}
+            taskTypeOptions={taskTypeOptions}
+            onTaskTypeOptionsSelect={jest.fn()}
+            allowContextWindowLength={false}
+          />
+        </MockFormProvider>
+      );
+
+      const inputField = screen.getByTestId('inference-endpoint-input-field');
+      expect(inputField).toBeInTheDocument();
+    });
+  });
+});