Add app repair for diagnostic failures/warnings

Helps #2399 (closed).

• diagnostics: Add optional component_id to DiagnosticCheck
• app, component: Add repair method
  • Allows apps and component to implement custom repair methods.
  • Default implementation asks relevant components to repair, and then if needed, requests re-run setup for the app.
  • Component.repair will return True by default, indicating that setup should be re-run.
• setup: Add method to run app repair
  • Repair is run within an operation.
  • Diagnostics are run for the app first.
  • Call app.repair, then re-run setup if needed.
  • Add helper functions for apps or components to store error messages in thread local storage. These error messages are shown at the end.
• diagnostics: Change "Re-run setup" to "Try to repair"
• letsencrypt: Re-obtain certificates during repair
  • Set check_id and domain for domain diagnostic check
  • In case of failing domain, try to re-obtain the certificate.
  • If there is an error, store it in thread local storage.
  • Any other failing diagnostic checks are handled by default implementation.
• letsencrypt: Fix diagnostic warning when no names configured

Tests:

• Run repair for warnings due to new package version available. Repair is completed successfully.

• Set an invalid domain name, and run repair for Let's Encrypt. Repair is completed and error is shown.

Signed-off-by: James Valleroy jvalleroy@mailbox.org