Separate Markdown processing from permissions

Right now we can't cleanly cache Markdown's resulting HTML because the author might reference something that the viewer doesn't have permission to view.

Continues discussion from !911 (merged)

/cc @DouweM @dzaporozhets

@dzaporozhets Were you thinking that we allow all references regardless of user permission, and then go back and alter the cached output later dynamically based on the current user?

@rspeicher Valery already created an issue to discuss how to handle the caching.
Want to use that one so we don't split the discussion between several issues?
See #2054 (closed)

@haynes Woops, thank you.

Status changed to closed

Were you thinking that we allow all references regardless of user permission, and then go back and alter the cached output later dynamically based on the current user?

@rspeicher We've got the same idea :) https://gitlab.com/gitlab-org/gitlab-ce/issues/2054#note_1673225

@rspeicher yes your idea is nice