feat: use explicit user/group id in container image

[reubenmiller]

Proposed changes

Use explicit user/group ids in the docker image to enable more predicatable behaviour across different build systems and images.

References

• https://www.docker.com/blog/understanding-the-docker-user-instruction/

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[Ruadhri17]

Checked with docker instructions and addgroup/adduser instructions for Alpine. LGTM

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
504	0	2	504	100	1h29m3.729053s