For the sake of better documentation for developers, I suggest following Hammer CLI scheme and moving our How to create a plugin page to core’s github repo.
Advantages:
Let’s put it to vote:
0 voters
Of course other suggestions are welcome too.
I like this and I think we should do the same for the proxy while we’re at it. I’d even be open to going as far as fully deprecating the wiki but that’s probably not in the scope of this suggestion 
I think the best place is actually in the theforeman.org website, we have various other “developer oriented” documentation there, and it’s much more visible than a markdown file inside the core repo which isn’t quite viewable from anywhere.
I think that it should be in three places.
Create a skelaton like foreman plugin that is a guide on how to do it, and several branches that demonstrate different things (or different repos).
Having a menu on the wiki and discourse for foreman resources that it’s one of them.
The foreman_plugin_template repo already exists and is the basis of the examples in the existing doc. It does not use separate branches, it just has examples of pretty much everything crammed in there 
@ekohl I can easily forsee a bunch of subcategories here along the lines of wiki/howtos/plugins/etc - it’s no better or worse than redmine technically, but would have better discoverability for end users
I would also prefer deprecating the wiki and moving all the content to the main page.
For the Plugin documentation it would mean replacing the link in Foreman :: Plugin Manuals with the full content of the wiki page. The Manual is already point to the Plugin documentation.
Redundant documentation typically results in only one version getting updates, so I would like to avoid it.
For the record: It looks like most of the people would like to see the documentation move to core.
Soon I will open a PR to core and a smaller PR to change the references in plugin section of the manual.