Added middleware docs

Author: syrusakbary

docs/execution/index.rst

@@ -0,0 +1,8 @@
+=========
+Execution
+=========
+
+.. toctree::
+   :maxdepth: 1
+
+   middleware

docs/execution/middleware.rst

@@ -0,0 +1,44 @@
+Middleware
+==========
+
+You can use ``middleware`` to affect the evaluation of fields in your schema.
+
+A middleware is any object that responds to ``resolve(*args, next_middleware)``.
+
+Inside that method, it should either:
+
+- Send ``resolve`` to the next middleware to continue the evaluation; or
+- Return a value to end the evaluation early.
+
+
+Resolve arguments
+-----------------
+
+Middlewares ``resolve`` is invoked with several arguments:
+
+- ``next`` represents the execution chain. Call ``next`` to continue evalution.
+- ``root`` is the root value object passed throughout the query.
+- ``args`` is the hash of arguments passed to the field.
+- ``context`` is the context object passed throughout the query.
+- ``info`` is the resolver info.
+
+
+Example
+-------
+
+This middleware only continues evaluation if the ``field_name`` is not ``'user'``
+
+.. code:: python
+
+	class AuthorizationMiddleware(object):
+		def resolve(self, next, root, args, context, info):
+			if info.field_name == 'user':
+				return None
+			return next(root, args, context, info)
+
+
+And then execute it with:
+
+.. code:: python
+
+	result = schema.execute('THE QUERY', middleware=[AuthorizationMiddleware()])

docs/index.rst

@@ -8,6 +8,7 @@ Contents:
 
    quickstart
    types/index
+   execution/index
    relay/index
 
 Integrations