[Internal]: [Cases] Added a new form field `additional fields`

[janmonschke]

Description

We're introducing a new field to the cases IBM resilient form that allows customers to set arbitrary fields on the IBM resilient case. See the linked PR for a screenshot and more information.

In this iteration of this feature, the customer will have to set the JSON values in a JSON editor. This is easy enough for primitives such as numbers, booleans and text fields. For select/multiselect/date fields, it is more complicated but we will improve that in the next release.

Resources

This feature was implemented in: elastic/kibana#236144

It is based on this enhancement request: https://github.com/elastic/enhancements/issues/23600

Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

Feature differences

Identical

What release is this request related to?

9.2

Serverless release

The week of Oct 21

Collaboration model

The documentation team

Point of contact.

Main contact: @janmonschke

Stakeholders: @melissaburpo