Improvement: Add client credentials location parameter for Client Credentials OAuth flow

[alexander-sil]

Description

I have developed a fix to make the user able to send OAuth client credentials (that is, client ID and secret) in the request body. The fix consists of an additional dropdown box to determine the authActions file flow.

Motivation and Context

Fixes #9711
This change is needed by niche use cases, e.g. when the partner client does not fully comply to the Section 2.3.1 of RFC 6479 standard - sometimes due to requiring the client to send the client credentials in the JSON body content. This is experienced by me first-hand, as I have to develop an API to integrate with such example of a service.

How Has This Been Tested?

Manual quality assurance (QA).

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.