Apply and document pip-compile (#119 #127)

I forgot to document this, and the updates to the requirements were
skipped in #127 as a result.

backend/README.md

@@ -26,6 +26,8 @@ python manage.py migrate # create the database
 python manage.py createsuperuser # ask to specify a new admin name, email and password
 ```
 
+If you need to update the requirements, edit the `requirements.in` (for application dependencies) or `requirements-test.in` (for test dependencies), then run `pip-compile requirements.in` and/or `pip-compile requirements-test.in` in order to update the corresponding `requirements{,-test}.txt`. This ensures that all pinned dependencies are compatible and that no dependencies linger around when they are no longer required.
+
 ## Running
 
 ```bash

backend/requirements-test.in

@@ -1,3 +1,3 @@
 pytest
-pytest-django<4
+pytest-django
 six

backend/requirements-test.txt

@@ -1,6 +1,6 @@
 #
-# This file is autogenerated by pip-compile with python 3.8
-# To update, run:
+# This file is autogenerated by pip-compile with Python 3.8
+# by the following command:
 #
 #    pip-compile requirements-test.in
 #

backend/requirements.txt

@@ -1,6 +1,6 @@
 #
-# This file is autogenerated by pip-compile with python 3.8
-# To update, run:
+# This file is autogenerated by pip-compile with Python 3.8
+# by the following command:
 #
 #    pip-compile requirements.in
 #
@@ -14,6 +14,8 @@ certifi==2022.9.24
     # via requests
 charset-normalizer==2.1.1
     # via requests
+defusedxml==0.7.1
+    # via sruthi
 django==4.1.2
     # via
     #   -r requirements.in
@@ -25,6 +27,8 @@ django-json-widget==1.1.1
     # via -r requirements.in
 djangorestframework==3.14.0
     # via -r requirements.in
+flatten-dict==0.4.2
+    # via sruthi
 future==0.18.2
     # via django-json-widget
 idna==3.4
@@ -36,11 +40,18 @@ psycopg2==2.9.4
 pytz==2022.4
     # via djangorestframework
 requests==2.28.1
-    # via -r requirements.in
+    # via
+    #   -r requirements.in
+    #   sruthi
+six==1.16.0
+    # via flatten-dict
 soupsieve==2.3.2.post1
     # via beautifulsoup4
 sqlparse==0.4.3
     # via django
+sruthi==1.0.0
+    # via -r requirements.in
 urllib3==1.26.12
     # via requests
-sruthi==1.0.0
+xmltodict==0.13.0
+    # via sruthi