- Add integration test for serving cert auto-generation and rotation
- Add unit test for `WithInitialEvent` of the cert manager controller
- Move UpdateAPIService() into the `apicerts` package, since that is
the only user of the function.
- Refactors the existing cert generation code into controllers
which read and write a Secret containing the certs
- Does not add any new functionality yet, e.g. no new handling
for cert expiration, and no leader election to allow for
multiple servers running simultaneously
- This commit also doesn't add new tests for the cert generation
code, but it should be more unit testable now as controllers
