Testing experimental versions of Gitea

[realaravinth]

@dachary

Since tests will eventually need to run in a CI, using LE is impractical, but setting up an ownca certificate authority, although not a oneliner, is not very complicated once you have an example to follow.

Is there a reason why a certificate authority like LE is required for testing? Is it just to issue trusted certs or does it play a role in federation too?