fix(kafka-connect): call .get() on basicAuth Supplier fields in KafkaConnectApiFactory

[Yoni-Weisberg]

Summary

KafkaConnectClientConfig.basicAuthUser() and basicAuthPassword() return Supplier<String> — the record accessor returns the supplier object, not the resolved string. Concatenating them without .get() embeds the lambda toString() into the Authorization header:

Authorization: Basic aW8uamlra291LmthZmthLmNvbm5lY3QuYXBpLkthZmthQ29ubmVjdENsaWVudENvbmZpZyQkTGFtYmRh...

Decoded, that's something like:

io.jikkou.kafka.connect.api.KafkaConnectClientConfig$$Lambda/0x0000...@...:io.jikkou...$$Lambda/...@...

The Connect REST API rejects this with HTTP 401 Unauthorized.

Fix: call .get() on both suppliers in getAuthorizationHeader().

This is the same class of bug fixed for the Schema Registry provider in 0b5c775.

Changes

• KafkaConnectApiFactory.java: add .get() on config.basicAuthUser() and config.basicAuthPassword()
• KafkaConnectApiFactoryTest.java: new test that starts a MockWebServer, makes a real HTTP request, and asserts the Authorization header encodes the actual credentials
• pom.xml: add mockwebserver test dependency (same pattern as jikkou-provider-schema-registry)

Test plan

• KafkaConnectApiFactoryTest#shouldBuildBasicAuthHeaderFromActualCredentials passes with the fix
• Reverting the fix causes the test to fail with a header containing the lambda toString() rather than alice:secret

Fixes #758.

🤖 Generated with Claude Code

[fhussonnois]

Look good to me! Thank you very much for this contribution.