Adding support for production grade image in Dockerfile

[anushka159-a]

I have modified the current Dockerfile to be able to generate a Production grade Docker Image based on UBI, the new Dockerfile follows the below good practices for Production.

Multi-stage build: keeps the final image small and clean.
Non-root execution: creates appuser (uid 10001) and runs the service as non-root.
Minimal runtime dependencies: no extra tools/packages installed (keeps attack surface small).
Metadata labels: provides traceability (name, version, maintainer, vendor, etc.).
Deterministic build: dependencies are pulled in the build stage, final image only has the binary.
Absolute path: in ENTRYPOINT: safer for production.

[pasquale95]

@anushka159-a please enhance the Dockerfile and .dockerignore files to follow the guidelines we discussed during our sync.

[pasquale95]

@cendhu I've updated the PR with some improvements. I have a couple of questions:

• the Docker README is outdated and technically not necessary anymore since it refers to internal IBM procedures. Should we remove it with this PR?
• the docker-compose is also outdated as it refers to when the images were splitted. I suggest to either remove or update it. If you're ok with removing it, i can do it with this PR.
• I see in many code places that by default the version 0.0.2 is referred. Is this intended or should they point always to the latest?

[pasquale95]

LGMT
Not true. Pipeline failed.

Pipeline failing on new prod-ready images.

[pasquale95]

LGTM