* caddytls: Support multiple issuers
Defaults are Let's Encrypt and ZeroSSL.
There are probably bugs.
* Commit updated integration tests, d'oh
* Update go.mod
* httpcaddyfile: Revise automation policy generation
This should fix a frustrating edge case where wildcard subjects are
used, which potentially get shadowed by more specific versions of
themselves; see the new tests for an example. This change is motivated
by an actual customer requirement.
Although all the tests pass, this logic is incredibly complex and
nuanced, and I'm worried it is not correct. But it took me about 4 days
to get this far on a solution. I did my best.
* Fix typo
