refactor: Simplify entity registration code flow

[albinsuresh]

Proposed changes

Refactor the entity registration and auto registration code for simplicity and improved readability.

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

[albinsuresh]

This test isn't valid anymore, since caching of unregistered entity data as "pending entity data" was implemented.

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
440	0	3	440	100	1h1m11.111427s

[codecov]

Codecov Report

Attention: Patch coverage is 79.16667% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 78.0%. Comparing base (b3c84af) to head (c53e14a).
Report is 10 commits behind head on main.

Additional details and impacted files

Files	Coverage Δ
crates/extensions/c8y_mapper_ext/src/converter.rs	83.6% <79.1%> (-0.4%)	⬇️

... and 13 files with indirect coverage changes

[albinsuresh]

Instead of this, I'd like to update EntityRegistrationMessage::try_from to return a proper error. It is currently returning () as the error type, which is weird. Not quite sure it was done like that in the past. I'm assuming there was some concrete reason behind it.

[rina23q]

I'd like to update EntityRegistrationMessage::try_from to return a proper error.

I vote for it.

The current error is translated to ConversionError::UnexpectedError eventually, but I think receiving invalid entity registration message is not really "unexpected". For example, if someone publishes to the topic te/custom/four/segments/topic, the current code goes to this error.

[didier-wenzek]

I'd like to update EntityRegistrationMessage::try_from to return a proper error.

Indeed, better.

[rina23q]

Thanks Albin, looks very good. Now much easier to understand.

[rina23q]

I'd like to update EntityRegistrationMessage::try_from to return a proper error.

I vote for it.

The current error is translated to ConversionError::UnexpectedError eventually, but I think receiving invalid entity registration message is not really "unexpected". For example, if someone publishes to the topic te/custom/four/segments/topic, the current code goes to this error.