The core of my Java application is in place, yet the server-side logic needs to be rounded out so the product can move into full testing. I have the existing codebase, build scripts, and unit-test framework ready in a Git repository; you will be working exclusively on the backend, adding the missing feature set and wiring it cleanly into what already exists. The current stack uses plain Java 17 with Maven, JUnit tests, and a small in-memory database for quick runs. Your mission is to create the remaining service classes, refactor any brittle sections you spot along the way, and commit code that compiles, passes the test suite, and follows the same formatting conventions already in the project. Deliverables • New or updated Java classes covering the requested backend functionality • Corresponding unit tests with meaningful assertions • A concise README note explaining build steps and new endpoints or public methods I’ll merge your pull request once the tests are green and the code review shows no regressions. If you have questions about edge cases or need sample payloads, ping me on the repo ticket board and I’ll respond quickly so you can keep moving.