add instructions for django

Author: vegu

docs/django.md

@@ -0,0 +1,50 @@
+# Django Requirements
+
+When generating api-documentation for django projects it will likely complain that django is not configured during the generation process.
+
+
+## Create a file called `pymdgen_init.py`
+
+This should be created in the same place as all the other source code files.
+
+```py
+import logging
+
+logger = logging.getLogger("django")
+
+try:
+
+    # This is to be included in doc *.md files that
+    # render api documentation for django models
+    # requiring django environment to be setup (app configure etc.)
+    #
+    # There appears to be no good check on whether this has happened
+    # yet or not, in the case of setup being called again an
+    # exception will be raised that we catch and ignore
+
+    import django
+
+    django.setup()
+
+except Exception as exc:
+
+    logger.error(f"exception during django-setup for pymdgen: {exc}")
+
+
+```
+
+## Attach it to pymdgen doc files that generate django code
+
+Any md file that calls `pydmgen` on django code needs to also call `pymdgen` on this new module.
+
+So for example
+
+```
+{pymdgen:my_django_app.module}
+```
+
+becomes
+
+```
+{pymdgen:my_django_app.pymdgen_init}{pymdgen:my_django_app.module}
+```