Document logging to files

[uniqueg]

Is your feature request related to a problem? Please describe.

Currently, app and worker logs are streamed to STDERR by default. While this guarantees easy access to logs by devops/administrators, logs are not persisting when the service is re-deployed. It may also be harder to find and analyze logs.

Describe the solution you'd like

Different logging handlers can be configured via cwl_wes/config/log_config.yaml. Document how logging to files, as well as a basic log rotation scheme can be configured.

Describe alternatives you've considered
N/A

Additional context
For log rotations, consider how overflowing volumes can be avoided given a configured volume size for the service. This may require code changes.

[uniqueg]

This issue should should be handled in FOCA instead, as the log configuration will move there eventually (#153).