Add transports based on Azure PaaS (#891)

* Add transports based on Azure PaaS

This pull request adds two new transport implementations:

- `azurestoragequeues` is implemented on top of Azure Storage
  Queues [1]. This offers a simple but scalable and low-cost PaaS
  transport for Celery users in Azure. The transport is intended to be
  used in conjunction with the Azure Block Blob Storage backend [2].

- `azureservicebus` is implemented on top of Azure Service Bus [3] and
  offers PaaS support for more demanding Celery workloads in Azure. The
  transport is intended to be used in conjunction with the Azure
  CosmosDB backend [4].

This pull request was created together with @ankurokok, @dkisselev,
@evandropaula, @martinpeck and @michaelperel.

[1] https://azure.microsoft.com/en-us/services/storage/queues/
[2] https://github.com/celery/celery/pull/4685
[3] https://azure.microsoft.com/en-us/services/service-bus/
[4] https://github.com/celery/celery/pull/4720

* Exclude Azure transports from code coverage

There is test coverage for the transports but the tests require Azure
credentials to run (passed via environment variables) so codecov doesn't
exercise them.

* Remove env vars to configure transport

* Remove abbreviations

4 files changed, 54 insertions, 1 deletions

diff --git a/docs/includes/introduction.txt b/docs/includes/introduction.txt
index 2cbee3c2..a4fc4f0a 100644
--- a/docs/includes/introduction.txt
+++ b/docs/includes/introduction.txt
@@ -35,7 +35,8 @@ Features
 
     * Virtual transports makes it really easy to add support for non-AMQP
       transports. There is already built-in support for `Redis`_,
-      `Amazon SQS`_, `ZooKeeper`_, `SoftLayer MQ`_ and `Pyro`_.
+      `Amazon SQS`_, `Azure Storage Queues`_, `Azure Service Bus`_,
+      `ZooKeeper`_, `SoftLayer MQ`_ and `Pyro`_.
 
     * In-memory transport for unit testing.
 
@@ -62,6 +63,8 @@ and the `Wikipedia article about AMQP`_.
 .. _`qpid-python`: https://pypi.org/project/qpid-python/
 .. _`Redis`: https://redis.io/
 .. _`Amazon SQS`: https://aws.amazon.com/sqs/
+.. _`Azure Storage Queues`: https://azure.microsoft.com/en-us/services/storage/queues/
+.. _`Azure Service Bus`: https://azure.microsoft.com/en-us/services/service-bus/
 .. _`Zookeeper`: https://zookeeper.apache.org/
 .. _`Rabbits and warrens`: http://web.archive.org/web/20160323134044/http://blogs.digitar.com/jjww/2009/01/rabbits-and-warrens/
 .. _`amqplib`: http://barryp.org/software/py-amqplib/
diff --git a/docs/reference/index.rst b/docs/reference/index.rst
index 092429bc..471fe4f8 100644
--- a/docs/reference/index.rst
+++ b/docs/reference/index.rst
@@ -38,6 +38,8 @@
     kombu.asynchronous.aws.sqs.message
     kombu.asynchronous.aws.sqs.queue
     kombu.transport
+    kombu.transport.azurestoragequeues
+    kombu.transport.azureservicebus
     kombu.transport.pyamqp
     kombu.transport.librabbitmq
     kombu.transport.qpid
diff --git a/docs/reference/kombu.transport.azureservicebus.rst b/docs/reference/kombu.transport.azureservicebus.rst
new file mode 100644
index 00000000..881de039
--- /dev/null
+++ b/docs/reference/kombu.transport.azureservicebus.rst
@@ -0,0 +1,24 @@
+==================================================================
+ Azure Service Bus Transport - ``kombu.transport.azureservicebus``
+==================================================================
+
+.. currentmodule:: kombu.transport.azureservicebus
+
+.. automodule:: kombu.transport.azureservicebus
+
+    .. contents::
+        :local:
+
+    Transport
+    ---------
+
+    .. autoclass:: Transport
+        :members:
+        :undoc-members:
+
+    Channel
+    -------
+
+    .. autoclass:: Channel
+        :members:
+        :undoc-members:
diff --git a/docs/reference/kombu.transport.azurestoragequeues.rst b/docs/reference/kombu.transport.azurestoragequeues.rst
new file mode 100644
index 00000000..3ee0ef6d
--- /dev/null
+++ b/docs/reference/kombu.transport.azurestoragequeues.rst
@@ -0,0 +1,24 @@
+========================================================================
+ Azure Storage Queues Transport - ``kombu.transport.azurestoragequeues``
+========================================================================
+
+.. currentmodule:: kombu.transport.azurestoragequeues
+
+.. automodule:: kombu.transport.azurestoragequeues
+
+    .. contents::
+        :local:
+
+    Transport
+    ---------
+
+    .. autoclass:: Transport
+        :members:
+        :undoc-members:
+
+    Channel
+    -------
+
+    .. autoclass:: Channel
+        :members:
+        :undoc-members: