Add git integration to server

Adds git integration as in #71.

Let me know if I should squash all relevant commits into a single one.

The branch also contains some early commits of minor fixes I picked up along the way in my first few days exploring the codebase. Let me know if I should move them to a separate MR or remove them altogether.

requirements.txt

@@ -3,7 +3,7 @@ argon2-cffi==20.1.0		# 2021-07-18 Password hashing algorithm
 Babel==2.9.1			# 2022-01-23
 Django==3.2.18			# 2023-05-06
 feedparser~=6.0.8     # Check: not updated since 2016. [JdW, 2021-09-25] Upgrade to v6; v5 fails.
-psycopg2==2.8.6	  		# 2020-09-19 PostgreSQL engine
+psycopg2==2.9.5	  		# 2020-09-19 PostgreSQL engine -- 2023-05-10 update for python 3.11
 pytz==2021.3			# 2022-11-18 Timezone package
 # djangorestframework==3.9.3	# DEPREC, see next entry -- 2019-12-05  IMPORTANT: update templates/rest_framework/base.html if corresponding file rest_framework/templates/rest_framework/base.html has changed
 git+https://github.com/SciPost/django-rest-framework.git@bootstrap-v5