Enable Middleware Support for Blueprint Groups (#1399)

* enable blueprint group middleware support

This commit will enable the users to implement a middleware at the
blueprint group level whereby enforcing the middleware automatically to
each of the available Blueprints that are part of the group.

This will eanble a simple way in which a certain set of common features
and criteria can be enforced on a Blueprint group. i.e. authentication
and authorization

This commit will address the feature request raised as part of Issue #1386

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* enable indexing of BlueprintGroup object

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* rename blueprint group file to fix spelling error

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* add documentation and additional unit tests

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* cleanup and optimize headers in unit test file

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* fix Bluprint Group iteratable method

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* add additional unit test to check StopIteration condition

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* cleanup iter protocol implemenation for blueprint group and add slots

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* fix blueprint group middleware invocation identification

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* feat: enable list behavior on blueprint group object and use append instead of properly to add blueprint to group

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

docs/sanic/api_reference.rst

@@ -20,6 +20,15 @@ sanic.blueprints module
     :undoc-members:
     :show-inheritance:
 
+sanic.blueprint_group module
+----------------------------
+
+.. automodule:: sanic.blueprint_group
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+
 sanic.config module
 -------------------
 

docs/sanic/blueprints.md

@@ -127,7 +127,7 @@ Blueprints have almost the same functionality as an application instance.
 WebSocket handlers can be registered on a blueprint using the `@bp.websocket`
 decorator or `bp.add_websocket_route` method.
 
-### Middleware
+### Blueprint Middleware
 
 Using blueprints allows you to also register middleware globally.
 
@@ -145,6 +145,36 @@ async def halt_response(request, response):
 	return text('I halted the response')
 ```
 
+### Blueprint Group Middleware
+Using this middleware will ensure that you can apply a common middleware to all the blueprints that form the
+current blueprint group under consideration.
+
+```python
+bp1 = Blueprint('bp1', url_prefix='/bp1')
+bp2 = Blueprint('bp2', url_prefix='/bp2')
+
+@bp1.middleware('request')
+async def bp1_only_middleware(request):
+    print('applied on Blueprint : bp1 Only')
+
+@bp1.route('/')
+async def bp1_route(request):
+    return text('bp1')
+
+@bp2.route('/<param>')
+async def bp2_route(request, param):
+    return text(param)
+
+group = Blueprint.group(bp1, bp2)
+
+@group.middleware('request')
+async def group_middleware(request):
+    print('common middleware applied for both bp1 and bp2')
+    
+# Register Blueprint group under the app
+app.blueprint(group)
+```
+
 ### Exceptions
 
 Exceptions can be applied exclusively to blueprints globally.