User Story: Forward log messages of execution plane Keptn-services to Keptn core

As a user, I want to see error (log) message of my execution plane Keptn-services without having to use kubectl. Therefore, those error messages need to be forwarded to Keptn core.

Detail

Execution plane Keptn-services are usually started on Kubernetes and have a distributor as a sidecar. The service itself does not know about the sidecar, though it communicates with it via some REST API Endpoints (that are basically forwarded to Keptn control-plane).
Currently, log messages of the Keptn-service are just printed to stdout/stderr (depending on the logging framework). Those log messages can only be seen by calling kubectl -n some-namespace logs deployment/my-service my-service.

Proposal

Capturing errors can be done in the Distributor of a Keptn Service, which would capture error logs (sent to std::err) of the side-car container (the service) and forward them to the keptn control plane
❗ Note that calling the errors API shall be limited to one call per minute. (Implement throttler in go-utils)
❗ Beware of possible refactoring tasks in the distributor
❗ This operation must be allowed to fail (e.g. old Keptn version vs. new Distributor)

Definition of Done

• Error Log Messages of Keptn-services are forwarded to Keptn core in a way that does not require implementation changes in the Keptn-service.

Dependencies

#4032

Resources

• How to capture logs from as a side-car container https://superuser.com/a/1530503