Implement service_info endpoint

[kushagra189]

• Separate API specs are present for service_info endpoints. Add support accordingly.
• Put a section service_info in the endpoints config section and provide some dummy values for the defaults; then set these once when the service first starts on an empty database; they should not be updated on subsequent starts unless the config is changed; this behavior is implemented exactly in that way in cwl-WES, so we can just copy/paste the implementation from there pretty much. (Alex's reference and expectation)