PIL-1362 Update SubmitUktr to use header for pillar2Id

[JamesMMiller]

Summary

Added error handling and test cases for invalid JSON submissions to the UK Tax Return endpoint.

Changes

• Added custom JSON decoder action to handle invalid JSON payloads
• Added new error cases with corresponding test data:
  • 401 (Unauthorized)
  • 403 (Forbidden)
  • 404 (Not Found)
  • 415 (Unsupported Media Type)
  • 422 (Unprocessable Entity)
  • 500 (Internal Server Error)
• Updated README to use a table format for response scenarios

Testing

• Added test cases for each error scenario
• Added test for malformed JSON input

[platops-pr-bot]

• SBT can be updated to 1.9.9 in project/build.properties
• Your service can now use Java 21. Please set JavaType.OPENJDK_JRE21 in build-jobs - See confluence https://confluence.tools.tax.service.gov.uk/x/xIACM
• uk.gov.hmrc.sbt-auto-build can be updated to 3.24.0 in project/plugins.sbt
• STDOUT_IGNORE_NETTY appender (and usage) can be removed from conf/logback.xml - Netty server is no longer used (Since Play 2.6.x)
• ACCESS_LOG_FILE appender (and usage) can be removed from conf/logback.xml - it's never populated

[platops-pr-bot]

• SBT can be updated to 1.9.9 in project/build.properties
• uk.gov.hmrc.sbt-auto-build can be updated to 3.24.0 in project/plugins.sbt
• STDOUT_IGNORE_NETTY appender (and usage) can be removed from conf/logback.xml - Netty server is no longer used (Since Play 2.6.x)
• ACCESS_LOG_FILE appender (and usage) can be removed from conf/logback.xml - it's never populated
• Your service can now use Java 21. Please set JavaType.OPENJDK_JRE21 in build-jobs - See confluence https://confluence.tools.tax.service.gov.uk/x/xIACM