Validate logging for Mattermost

[Racer159]

Describe what should be investigated or refactored

We need to validate that logging is setup correctly for Mattermost when on top of uds-core and that we are capturing events from both the k8s components and the application level logs https://docs.sonarsource.com/sonarqube/latest/instance-administration/server-logs-and-system-info/.

We should also ensure that this validation is captured in the oscal-component.yaml file in the repo.

Links to any relevant code

https://github.com/defenseunicorns/uds-core/blob/164bf5f8bd58899f5ec1a179d6d409cfb46b850f/src/promtail/values/values.yaml#L6

Additional context

This should just using the logging/monitoring stack from uds-core