NIFI-15148 - Registry Clients - Support for branch creation (backend only)

[pvillard31]

Summary

NIFI-15148 - Registry Clients - Support for branch creation (backend only)

This PR takes the backend changes already submitted through #10471 and add support for all 4 flow registry clients. The UI changes would be done in a follow-up PR. This is in order to make it easier for reviewers and make progress for this improvement.

Tracking

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Issue Tracking

• Apache NiFi Jira issue created

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Build

• Build completed using ./mvnw clean install -P contrib-check
  • JDK 21
  • JDK 25

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