[Feature] Add DMARC munging support

[vstakhov]

We want Rspamd to be able to perform DMARC munging like Mailman does: https://mailman.readthedocs.io/en/release-3.1/src/mailman/handlers/docs/dmarc-mitigations.html

Probably not for embedded messages.

[vstakhov]

It is now has been implemented and tested in the actual mailing lists.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bjoe2k4]

@vstakhov Is the munging support designed for mailing list operators to fix dmarc issues for outgoing mail in case their mailing list software does not support munging - or rather for people on the receiving end of those broken messages to mitigate rejections?

[vstakhov]

The first - I've originally implemented it for mlmj software.

[janforth]

Trying to activate dmarc munging for my mm3 leaves me back with this error message:
2023-04-29 07:41:58 #426735(main) ; lua; lua_redis.lua:581: use default Redis settings for dmarc
2023-04-29 07:41:58 #426735(main) ; lua; dmarc.lua:534: dmarc reporting is enabled
2023-04-29 07:41:58 #426735(main) ; map; rspamd_map_add: added map /etc/rspamd/maps.d/dmarc_munging.inc
2023-04-29 07:41:58 #426735(main) ; lua; lua_maps_expressions.lua:125: cannot add maps combination for module dmarc: required elements are missing

What elements can be missing?