NIFI-15031 Remove historical fallback Remote PG registration requests

[exceptionfactory]

Summary

NIFI-15031 Removes historical fallback handling of unauthorized status responses in Remote Process Group communication.

NIFI-2578 added compatibility code for NiFi 1.0.0 to support sending a user registration request on authorization failures when communication with NiFi 0.7.0 and earlier. This fallback handling for unauthorized requests is no longer necessary in NiFi 2 and should be removed.

Changes include the removal of the RemoteNiFiUtils class, removing a reference to the shared WebClientUtils class.

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• Apache NiFi Jira issue created

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  • JDK 21
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[pvillard31]

Thanks for the cleanup @exceptionfactory