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A similar adapter can be used for RestClient (extends SslContextFactory.Client). 

Private code to drop / modify:

• drop current SSL utilities org.apache.kafka.connect.runtime.rest.util.SSLUtils with unit tests;

• simple refactoring SslFactory#instantiateSslEngineFactory to extract public static utility method to use inside RestServer.

Compatibility, Deprecation, and Migration Plan

Utilities are affected by the change: 

• ConnectStandalone;

• ConnectDistributed;

• MirrorMaker.

There is no impact on existing behavior, and  the existing behavior is not deprecated. All existing SSL properties are supported.

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Add integration tests to check:

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• RestClient creation (modify RestForwardingIntegrationTest);

• Custom SSL engine factory to configure RestServer listeners.

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