Added a bunch of developer documentation

docs/rest.rst

@@ -0,0 +1,37 @@
+REST API
+========
+
+.. toctree::
+   :titlesonly:
+   :maxdepth: 2
+   :caption: REST API
+   :hidden:
+
+InvenTree provides a REST API which serves data to the web client and also provides data access to third-party applications. The REST API is implemented using the `Django REST framework (DRF) <https://www.django-rest-framework.org/>`_ which provides the following features out of the box:
+
+* AJAX REST API
+* Web-browseable REST
+* User authentication 
+* Database model serialization and validation
+
+API Access
+----------
+
+The API is accessible from the root URL ``/api/``. It requires user authentication.
+
+* Requesting data via AJAX query will return regular JSON objects. 
+* Directing a browser to the API endpoints provides a web-browsable interface
+
+.. image:: _static/img/api_http.png
+
+API Documentation
+-----------------
+
+API documentation is provided by DRF autodoc tools, and is available for browsing at ``/api-doc/``
+
+.. image:: _static/img/api_doc.png
+
+API Code
+--------
+
+Javascript/jQuery code for interacting with the server via the REST API can be found under ``InvenTree/static/script/InvenTree``.