fix(#2445): add c8y proxy config settings

[Bravo555]

TODO

• documentation

Proposed changes

This PR adds c8y.proxy.client.host and c8y.proxy.client.port used to connect to running C8y HTTP proxy.

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

• use independent tedge.toml settings to access the c8y proxy server provided by tedge-mapper-c8y #2445

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

[codecov]

Codecov Report

Merging #2446 (eafe1b3) into main (02dc80d) will decrease coverage by 0.1%.
Report is 6 commits behind head on main.
The diff coverage is 73.0%.

Additional details and impacted files

Files	Coverage Δ
crates/extensions/c8y_mapper_ext/src/actor.rs	77.6% <ø> (+0.8%)	⬆️
crates/extensions/c8y_mapper_ext/src/tests.rs	91.6% <100.0%> (+<0.1%)	⬆️
crates/extensions/c8y_mapper_ext/src/converter.rs	81.1% <50.0%> (+<0.1%)	⬆️
.../tedge_config/src/tedge_config_cli/tedge_config.rs	82.0% <85.7%> (+<0.1%)	⬆️
crates/extensions/c8y_auth_proxy/src/url.rs	81.8% <66.6%> (ø)
crates/extensions/c8y_mapper_ext/src/config.rs	46.3% <33.3%> (+0.1%)	⬆️

... and 4 files with indirect coverage changes

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
359	0	3	359	100	55m17.061s

[jarhodes314]

If my understanding is correct, this should stress that the client settings configure the mapper and not the agent (which is what I, as a user, would assume the client setting changes as it is how the equivalent MQTT settings work). I guess the main clue as to this being the case without knowing the implementation details is that the c8y settings only affect the mapper as that's the only component that cares about Cumulocity.

[reubenmiller]

It is defining how clients can reach the endpoint.

The mapper is the only component that uses the setting directly, however the value of the setting will be used within command payloads which are consumed by other clients (e.g. custom device connectors)

[jarhodes314]

I get that, my point was "there isn't any point setting this on a child device as the value won't be used", which is unlike what happens for the mqtt client settings. It probably doesn't have much of an impact, but the logic behind why it's like that doesn't seem like a thing that's necessarily obvious to a user so might be worth drawing attention to.

[didier-wenzek]

I agree with @jarhodes314. We must be explicit telling that both c8y.proxy.bind.address and c8y.proxy.client.host have to be set on the box running the c8y mapper. The latter will be forwarded by the c8y mapper to its clients. c8y.proxy.client.host can also be directly set on the clients which aim to use the c8y REST API.

[Bravo555]

My bad, forgot about this ticket. Description tweaked in 0159f91, is it OK now?

[didier-wenzek]

Approved