fix: process pending Cumulocity IoT operations after network disconnections

[reubenmiller]

Proposed changes

Ensure any PENDING operations created in Cumulocity IoT whilst the bridge is down are processed upon reconnection with the cloud.

TODO

• System test to cover scenario. To help with the Rust development, the system test case includes a commented out "Workaround" which shows that publishing a message via tedge mqtt pub c8y/s/us 500 would "fix" the issue.
• Rust implementation

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

#3166

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

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
508	1	2	509	99.80	1h29m29.596549999s

Failed Tests

Name	Message	⏱️ Duration	Suite
Process any pending operations after connection disruptions	Expected operation (id=12993671) to be SUCCESSFUL, but got: PENDING (failureReason: )	175.425 s	Request Pending Operations