[FEATURE] add postfix check_policy_service support

[xpunkt]

Is your feature request related to a problem? Please describe.
if check_policy_service in postfix was supported, then wforce would have more data to use, and thus protect more

Describe the solution you'd like
i have no plans yet, if we just all could dream of 1 btc we would all be rich :)
but that would not stop abuse in mail ports

Describe alternatives you've considered
open-xchange if i just have the 1 btc

Additional context
postfix would be nice to see lua scripting in, it can imho only be made via check_policy_service or a custom milter, but to keep data foot print low i think at the start it would fit best in check_policy_service, with is the client and weakforced is then the server part of this, basicly as dovecot quota plugin that query if there is room for more mails

[neilcook]

Hmm, if only there was a way to open issues on the postfix repo...

[xpunkt]

is there code changes to postfix needed ?

[neilcook]

Oh I see, you want weakforced to implement a check_policy_service server? Hmm, looking at the spec https://www.postfix.org/SMTPD_POLICY_README.html I'm not sure this is the best fit for weakforced. At least it would require a reasonable amount of work - a new server that sits in-between postfix and wforce, and probably would also require the new wforce built-in API function that I've been thinking about to handle non-authentication related stuff (kind of like what you can do already with custom API endpoints, but built-in).