* move install_ssl_options_conf functionality to common
* add no cover
* compute current hash instead of saving
* make current hash be computed; switch to list of all canonical hashes
* put message directly into assertion
* don't pass logger
* add docstring
* Add unit tests for certbot.plugins.common.install_ssl_options_conf
Fixes#4559.
* Update options-ssl-nginx.conf in prepare, if it hasn't been modified.
* add previous options-ssl-nginx.conf hashes
* InstallSslOptionsConfTest
* remove .new file and only print warning once
* save digest to /etc/letsencrypt
* add comment reminding devs to update hashes
* add comment and test for sha256sum
* treat hash file as text file because python3
* move constants and rename hidden digest file