Add checks for RFC8460, SMTP-TLS reporting (TLSRPT) #881

[uwekamper]

This PR adds support for checking the policy record (e.g. _smtp._tls.example.com). The check parses the record and results in a "WARNING" state when the TLSRPT policy record is either nonexistant or malformed. To check if the TLSRPT record is well formed, we include a TLSRPT policy record parser in this PR.

The respective descriptions have been updated for both "en" and "nl" translations – though the "nl" translations needs to be looked over by a native speaker.

The test results UI has been updated to include the TLSRPT check on the results page (as part of 'Authenticity marks against phishing' section).

TLSRPT record broken or non-existing:

TLSRPT record exists and is well-formed:

[bwbroersma]

@mxsasha:

• Currently the parsing is using pyparsing: https://github.com/internetstandards/Internet.nl/blob/b886bccfe77b2dd7bd5a8c66475b764558a9125e/checks/tasks/tlsrpt_parsing.py#L26-L28

  We know at least using pyparsing like this does not work: https://github.com/internetstandards/Internet.nl/blob/1ae63936d609d59f17a4236a836d1dacd75a603e/checks/tasks/dmarc_parser.py#L45-L48

  because of #1114, so either this also does not work, or the DMARC code should change Optional to ZeroOrMore. BTW I also noted this regular expressions for parsing email addresses: https://github.com/internetstandards/Internet.nl/blob/b886bccfe77b2dd7bd5a8c66475b764558a9125e/checks/tasks/tlsrpt_parsing.py#L35-L39

  The weird thing is, this does not require a @, while I think is too restrictive in the mailbox part. Note the ABNF parsers are suggested in #1475.

• Would it be an option to also have a feature flag for a sub test, and maybe temporarily hide it by default? Currently that's only there for complete checks (not sub tests): https://github.com/internetstandards/Internet.nl/blob/1ae63936d609d59f17a4236a836d1dacd75a603e/internetnl/settings.py#L99-L107

  I know there was interest from the Netherlands governmental e-mail community to sign up TLSRPT for the comply-or-explain list. I'm unsure if this is done and what is the current state, at least it's not taken into the procedure yet (because I would be involved with that).