Authorization Documentation Updates (#740)

* add specification section on authentication and authorization in docs

* add notes on using the built in django auth and multi-tenant approach

docs/guide/src/SUMMARY.md

@@ -4,6 +4,7 @@
   - [About e-Manifest](e-Manifest.md)
 - [Project Design](design/source-roadmap.md)
   - [Repo Roadmap](design/source-roadmap.md)
+  - [Authentication & Authorization](design/auth.md)
   - [Source Design Document](design/sdd.md)
     - [Http Server Design](design/server.md)
     - [Client Design](design/browser-client.md)

docs/guide/src/design/auth.md

@@ -0,0 +1,55 @@
+# Authentication and Authorization
+
+This project makes extensive use of the Django authentication and authorization system.
+This document does not provide a overview of Django's auth systems, for more information,
+see the [Django documentation](https://docs.djangoproject.com/en/5.0/topics/auth/).
+
+## Authentication
+
+This project makes use of Django's built-in authentication system `django.contrib.auth` and the
+packages in the Django ecosystem (e.g., `django-allauth`) to authenticate users.
+
+We do not rely on external authentication services for this project to keep the project focused,
+avoid condoning a third-party service (as the U.S. government). This also provides an
+opportunity to demonstrate how systems can implement auth to use features of the e-Manifest system
+such as the Remote Signer policy and generally allowing their internal users electronically manifest
+without having an account in the US EPA's RCRAInfo/e-Manifest system.
+
+## Authorization
+
+Authorization is relatively complex for this project. Access to a resources (e.g., a manifest)
+is a dynamic process and needs to be determined on a per-user + per-role +
+per-object + per-object status basis.
+
+As an example scenario, a user wants to edit a manifest. The following applies:
+
+1. The user must be authenticated.
+2. The user must have access to a site listed on the manifest.
+3. The user must have the appropriate role/permission to edit the manifest.
+4. The manifest must be in a status that allows editing.
+5. The specific edits must be allowed by e-Manifest.
+
+### Python/Django Implementation Notes
+
+The Django framework ships with a built-in authentication and authorization system.
+The components of this built in system are found
+under the `django.contrib.auth` package. Leveraging the built-in system would allow us to
+take advantage of the many features that Django (such as the admin interface) provides and would
+ensure that we are using a well-tested, battle-hardened system.
+
+However, to quote
+[Customizing Django Authentication docs](https://docs.djangoproject.com/en/stable/topics/auth/customizing/#handling-object-permissions),
+
+> Django’s permission framework has a foundation for object permissions, though there is no implementation for it in the
+> core. That means that checking for object permissions will always return False or an empty list (depending on the
+> check performed). An authentication backend will receive the keyword parameters obj and user_obj for each object
+> related authorization method and can return the object level permission as appropriate.
+
+Object level permissions is a required feature for this project. There are 2 noteworthy packages
+that aim to provide object level permissions:
+
+1. [django-guardian](https://django-guardian.readthedocs.io/en/stable/)
+2. [django-rules](https://github.com/dfunckt/django-rules)
+
+As of this writing, the django-guardian package is mature, and widely used. However, it is not actively maintained.
+The django-rules package is actively maintained, but it is not as widely used as django-guardian.