Use serde tag enum representation for CommandStatus

[didier-wenzek]

As suggested by @Bravo555 with #2245 (comment), the reason field makes sense only for a Failed command.

Proposed changes

Attached the reason field to the only case where it makes sense: a Failed command.

#[derive(Debug, Deserialize, Serialize, PartialEq, Eq, Clone)]
#[serde(rename_all = "camelCase", tag = "status")]
pub enum CommandStatus {
    Init,
    Executing,
    Successful,
    Failed { reason: String },
}

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

[codecov]

Codecov Report

Merging #2290 (90d05dd) into main (3ba5851) will decrease coverage by 0.1%.
The diff coverage is 66.6%.

Additional details and impacted files

Files Changed	Coverage Δ
...tedge_agent/src/tedge_operation_converter/tests.rs	90.5% <ø> (-0.2%)	⬇️
crates/extensions/c8y_mapper_ext/src/converter.rs	77.8% <0.0%> (-0.1%)	⬇️
...rates/extensions/tedge_config_manager/src/actor.rs	69.4% <0.0%> (ø)
crates/extensions/tedge_log_manager/src/actor.rs	69.2% <0.0%> (ø)
crates/core/tedge_api/src/messages.rs	92.3% <66.6%> (+0.2%)	⬆️
...ates/core/tedge_agent/src/restart_manager/tests.rs	93.9% <100.0%> (-0.2%)	⬇️
crates/extensions/c8y_mapper_ext/src/log_upload.rs	76.5% <100.0%> (ø)
...rates/extensions/tedge_config_manager/src/tests.rs	91.9% <100.0%> (ø)
crates/extensions/tedge_log_manager/src/tests.rs	92.2% <100.0%> (ø)

... and 4 files with indirect coverage changes

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
288	0	3	288	100	1h0m25.244s

[rina23q]

LGTM