Refactor discourse puppet module to enable more general use

[kzar]

Background

The discourse puppet module in the infrastructure repository was designed to provision the intraforum server. We now want to run at least one other Discourse server and therefore need to generalise the module to allow that.

What to change

Anything that prevents the module from being used for a different forum running on a different server. Also the use of the module will likely need to change in the intraforum manifest, to pass in any new parameters that will now be required.

The init-discourse Python script in the module might need to be replaced / refactored to facilitate this. Ideally the logic would be completely replaced with Puppet but maybe that's not possible / practical.

Notes

The aim of this ticket is to allow us to continue testing of the phpBB to Discourse forum migration in ticket #1327. It would be wise to look at the changes already made to the infrastructure repository for this issue ​https://github.com/kzar/adblockplus-infrastructure/tree/1327-forum-migration when making the changes required.

It might even be desirable to fork that branch directly when working on the changes, as some have been started IIRC. A code review patchset could then be made against master.