NIFI-15214 Refactor site-to-site-client using Java HttpClient

[exceptionfactory]

Summary

NIFI-15214 Refactors the nifi-site-to-site-client module and the SiteToSiteRestApiClient class using the Java HttpClient, replacing and removing dependencies on synchronous and asynchronous Apache HttpClient 4 libraries.

The refactored implementation includes a new unit test for the SiteToSiteRestApiClient that exercises public HTTP methods with OkHttp MockWebServer. Updates include moving URL string parsing to a separate ClusterUrlParser class.

Additional changes include refactoring the ClusterLoadBalanceAuthorizer to remove usage of the Apache HttpClient DefaultHostnameVerifier, adding direct comparison of wildcard-prefixed client certificate DNS Subject Alternative Names, with new unit tests to verify positive and negative checks.

These changes enable removing Apache HttpClient 4 dependencies from the nifi-framework-nar and framework modules.

Tracking

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• Apache NiFi Jira issue created

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Build

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

Licensing

• New dependencies are compatible with the Apache License 2.0 according to the License Policy
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[pvillard31]

Have tested multiple scenarios with Site-to-Site, secured and non secured, everything seems to be working as expected. Merging, thanks for the refactoring @exceptionfactory !