Custom form: 404 if form does not exist.

Previously it encountered uncaught exception and had 500 error.
Merge pull request #1033 from learning-unlimited/form404

Custom form: 404 if form does not exist.
Bumps Django debug toolbar version
Changes debug toolbar settings to work around bugs
Merge pull request #1034 from learning-unlimited/debug-toolbar-version-bump

Bumps Django debug toolbar version
Merge remote-tracking branch 'origin/mit-prod' into main