https://sourceforge.net/p/forge/documentation/Allura%20API/ should gain some docs on the discussion API added in [#5650]
For bonus points, move/convert these docs into Allura itself, and change that wiki page to explain how SourceForge runs on Allura and reference the allura docs.
https://sourceforge.net/p/forge/documentation/Allura%20API/#discussion-forums
Didn't move docs at this point, since that'd require converting them from Markdown to rst