Add validation for required dashboard fields (#3761)

## Summary

This PR adds validation to ensure dashboards have both required fields:
`display_name` (name) and `warehouse_id`. The validation returns
**errors** (not warnings) for missing required fields, preventing
deployment until they are added.

## Changes

**bundle/config/validate/required.go:**
- Split `Apply()` method into two helper functions:
- `warnForMissingFields()` - Validates fields based on OpenAPI spec
annotations (existing behavior)
- `errorForMissingFields()` - Bespoke validation for fields not marked
as required in SDK/OpenAPI
- Added dashboard-specific validation in `errorForMissingFields()`:
  - Checks `display_name` is not empty
  - Checks `warehouse_id` is not empty
- Updated `Apply()` to call `errorForMissingFields()` first, then
`warnForMissingFields()`

## Why This Change?
These fields are marked as required in Terraform:
https://github.com/databricks/terraform-provider-databricks/blob/0c0272a8ae678a12e6d7c106245b083d10ba5e07/dashboards/resource_dashboard.go#L33

Adding this here has to benefits:
1. catch missing values without needing to go to Terraform or waiting
for deployment. These will surface early during bundle validate.
2. We ensure that these fields remain required for direct deployment.

## Test Coverage

New acceptance tests

---------

Co-authored-by: Claude <[email protected]>

Author: shreyas-goenka

acceptance/bundle/generate/dashboard-inplace/databricks.yml

@@ -5,5 +5,5 @@ resources:
   dashboards:
     test_dashboard:
       display_name: "test dashboard"
-      warehouse_id: ""
+      warehouse_id: "my-warehouse-1234"
       file_path: ./dash.lvdash.json

acceptance/bundle/generate/dashboard-inplace/output.txt

@@ -20,7 +20,8 @@ Deployment complete!
   "parent_path":"/Users/[USERNAME]/.bundle/dashboard update inplace/default/resources",
   "path":"/Users/[USERNAME]/.bundle/dashboard update inplace/default/resources/test dashboard.lvdash.json",
   "serialized_dashboard":"{\"a\":\"b\"}",
-  "update_time":"[TIMESTAMP]Z"
+  "update_time":"[TIMESTAMP]Z",
+  "warehouse_id":"my-warehouse-1234"
 }
 
 === update the dashboard file using bundle generate

acceptance/bundle/sync/databricks.yml

@@ -2,6 +2,7 @@ resources:
   dashboards:
     dashboard1:
       display_name: My dashboard
+      warehouse_id: "my-warehouse-1234"
 
 sync:
   exclude:

acceptance/bundle/sync/dryrun/databricks.yml

@@ -2,3 +2,4 @@ resources:
   dashboards:
     dashboard1:
       display_name: My dashboard
+      warehouse_id: "my-warehouse-1234"

acceptance/bundle/validate/dashboard_defaults/databricks.yml

@@ -4,18 +4,34 @@ workspace:
 resources:
   dashboards:
     empty_string:
+      warehouse_id: "my-warehouse-1234"
+      display_name: "empty-string"
+
       # unchanged
       parent_path: ""
 
     non_empty_string:
+      warehouse_id: "my-warehouse-1234"
+      display_name: "non-empty-string"
+
       # unchanged
       parent_path: "already-set"
 
     other_fields:
+      warehouse_id: "my-warehouse-1234"
       display_name: hello
+
       # parent_path set default
 
     set_to_true:
+      warehouse_id: "my-warehouse-1234"
+      display_name: "set-to-true"
+
       embed_credentials: true
 
-    completely_empty: {}
+    neither_parent_path_nor_embed_credentials:
+      warehouse_id: "my-warehouse-1234"
+      display_name: "neither-parent-path-nor-embed-credentials"
+
+      # parent_path set default
+      # embed_credentials set default

acceptance/bundle/validate/dashboard_defaults/output.txt

@@ -1,18 +1,17 @@
 {
-  "completely_empty": {
-    "embed_credentials": false,
-    "parent_path": "/Workspace/foo/bar"
-  },
   "empty_string": {
     "embed_credentials": false,
     "parent_path": ""
   },
+  "neither_parent_path_nor_embed_credentials": {
+    "embed_credentials": false,
+    "parent_path": "/Workspace/foo/bar"
+  },
   "non_empty_string": {
     "embed_credentials": false,
     "parent_path": "already-set"
   },
   "other_fields": {
-    "display_name": "hello",
     "embed_credentials": false,
     "parent_path": "/Workspace/foo/bar"
   },

acceptance/bundle/validate/dashboard_defaults/script

@@ -1 +1 @@
-$CLI bundle validate -o json | jq .resources.dashboards
+$CLI bundle validate -o json | jq '.resources.dashboards | map_values({embed_credentials: .embed_credentials, parent_path: .parent_path})'

acceptance/bundle/validate/dashboard_required_name/databricks.yml

@@ -0,0 +1,6 @@
+resources:
+  dashboards:
+    # Missing display_name (name)
+    my_dashboard:
+      warehouse_id: "test"
+      serialized_dashboard: "{}"

acceptance/bundle/validate/dashboard_required_name/out.test.toml

@@ -0,0 +1,15 @@
+
+>>> [CLI] bundle validate
+Error: dashboard display_name is required
+  at resources.dashboards.my_dashboard
+  in databricks.yml:6:7
+
+Name: test-bundle
+Target: default
+Workspace:
+  User: [USERNAME]
+  Path: /Workspace/Users/[USERNAME]/.bundle/test-bundle/default
+
+Found 1 error
+
+Exit code: 1