AMP-187 Add api test as a separate module in project which can be inv…

[samirgarg]

Add api test as a separate module in project which can be invoked from commandline and intellij

AMP-187 Create API tests for Subscription service

Summary

• Configured apiTest as a standalone Gradle project with its own build.gradle (not a subproject)
• Change Docker Compose build context to reference the root project's Dockerfile and JAR
• Created buildRootBootJar task to build the root project's bootJar before Docker image creation
• Optimized build configuration for a test-only module (disabled main source set and unnecessary tasks)
• Created README.md with prerequisites, test execution instructions, troubleshooting, and report locations
• Removed earlier apiTests which were now duplicate