ENH: introduce JSON converter

Summary

For https://gitlab.indiscale.com/caosdb/customers/leibniz-zmt/management/-/issues/46. Create a converter that reads a JSON file.

Focus

Some new converters and a lot of fixes on the way.

Test Environment

Some new unit tests, use ZMT example for manual testing.

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• [ ] All automated tests pass
• Reference related issues
• [ ] Up-to-date CHANGELOG.md (or not necessary)
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• [ ] All automated tests pass
• [ ] Up-to-date CHANGELOG.md (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.