[MD]Fix schema for test connection to separate validation based on auth type

[BionIT]

Description

This change refactors the schema validation for test connection API to separate the validation based on auth type. Tests were added for no auth, sigv4 and basic auth.

Issues Resolved

Fixes #5987

Screenshot

fixschema.mp4

Testing the changes

The following steps were performed:

1. enable data source plugin
2. before the change, test connection would fail for no auth at the time of creation
3. before the change, test connection would succeed for no auth after creation
4. after the fix, test connection is successful for no auth at the time of creation and after creation
5. after the fix, test connection is successful for basic auth at the time of creation and after creation
6. after the fix, test connection is successful for sigv4 auth at the time of creation and after creation

Check List

• All tests pass
  • yarn test:jest
  • yarn test:jest_integration
• New functionality includes testing.
• New functionality has been documented.
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

[bandinib-amzn]

First I thought we can skip ChangeLog. But it is bug fix, so we should add in ChangeLog, right? @BionIT What do you think?

[BionIT]

First I thought we can skip ChangeLog. But it is bug fix, so we should add in ChangeLog, right? @BionIT What do you think?

Yeah, I added changelog to unreleased section in a new commit. Thanks @bandinib-amzn!