ACME modules refactor

[felixfontein]

SUMMARY

Some refactoring of module_utils/acme.py: split that monster up, and clean up some of the code. Then it splits up the ACMEAccount object into ACMEClient and ACMEAccount and improves the API w.r.t error handling. Finally it refactors the acme_certificate module to move certain code parts to module_utils.

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

acme module_utils
acme_certificate

[felixfontein]

recheck

[felixfontein]

I used this version to renew all my certificates, worked as expected. So the refactoring cannot be too butched :)

I also did some ACME v1 testing with BuyPass's staging endpoint, which also worked, and I did revoke the old certificates (also worked).

[felixfontein]

I closed #184 and #186, let's just continue with this one.

[felixfontein]

I've cleaned up the commit history a bit to make it easier to review commit by commit, which is probably a lot easier than reviewing the whole resulting diff.

If anyone would prefer this to be split up into multiple PRs to simplify reviewing, I can happily do that (again). Just tell me what your preferences are.

[rndmh3ro]

I tested the PR with our Let's Encrypt Collection (https://github.com/T-Systems-MMS/ansible-collection-letsencrypt/). Worked flawlessly.

[felixfontein]

Restarting tests for a last time, will merge tomorrow if they passed.

[felixfontein]

@bmm-alc @rndmh3ro thanks a lot for reviewing and testing!