Update Markdown extension code for Markdown 3.0 deprecations.
Review Request #11931 — Created Jan. 14, 2022 and submitted — Latest diff uploaded
Djblets 2.x is compatible with Markdown 3.x, but still used a lot of
Markdown 2.x semantics, including legacy processor registration and
extendMarkdown()function signatures. These trigger deprecation
warnings in Markdown 3.x.This updates our Markdown extension code to comply with the modern
requirements.
Unit tests pass on all supported versions of Python and Django.