add schema validation support for more json-schema version refs (closes #2354)

[philosomniac]

• [ ] Breaking change?

What changes did you make? Issue #2354 mentions that attempting to publish a message with schema validation will fail using a schema that references json-schema version draft-07. According to the Ajv docs, different json-schema versions (as referenced by the $schema property) require using different modules in Ajv. The current code always uses the draft-2020-12 module, which will throw errors if an earlier version of json-schema is referenced in the $schema property--so I added some code that will select the correct Ajv module based on the $schema property.

Is there anything you'd like reviewers to focus on? This is my very first open-source contribution--please be gentle! :)

How Has This Been Tested? (put an "x" (case-sensitive!) next to an item)

• [ ] No need to
• [ ] Manually (please, describe, if necessary)
• [x] Unit checks
• [ ] Integration checks
• [ ] Covered by existing automation

Checklist (put an "x" (case-sensitive!) next to all the items, otherwise the build will fail)

• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• [x] My changes generate no new warnings (e.g. Sonar is happy)
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged

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A picture of a cute animal (not mandatory but encouraged) As requested--my favorite dog breed :)

[Haarolean]

Hi @philosomniac, as this repo is no longer maintained (#4255), can I ask you to raise the same PR into our new repo (https://github.com/kafbat/kafka-ui)? Thank you