Add Integrations doc page with support matrix

Adds a new documentation section that descript which service
integrations are currently supported and their integrations status.
This information is not clear today and will help to cover the lack
of testing and documention about them.

Change-Id: I26b2a2ef5672b78a575a2bdaef3a08d5bbc063bd

doc/source/index.rst

@@ -42,6 +42,7 @@ specific prior release.
   user/index
   configuration/index
   contributor/plugin/index
+  integrations/index
   man/index
 
 .. toctree::

doc/source/integrations/index.rst

@@ -0,0 +1,126 @@
+============
+Integrations
+============
+
+The following table provides an Integration status with different services
+which Watcher interact with. Some integrations are marked as Supported,
+while others as Experimental due to the lack of testing and a proper
+documentations.
+
+Integration Status Matrix
+-------------------------
+
+    .. list-table::
+       :widths: 20 20 20 20
+       :header-rows: 1
+
+       * - Service Name
+         - Integration Status
+         - Documentation
+         - Testing
+       * - :ref:`Cinder <cinder_integration>`
+         - Supported
+         - Minimal
+         - Unit
+       * - :ref:`Glance <glance_integration>`
+         - Experimental
+         - Missing
+         - None
+       * - :ref:`Ironic <ironic_integration>`
+         - Experimental
+         - Minimal
+         - Unit
+       * - :ref:`Keystone <keystone_integration>`
+         - Supported
+         - Minimal
+         - Integration
+       * - :ref:`MAAS <maas_integration>`
+         - Experimental
+         - Missing
+         - Unit
+       * - :ref:`Neutron <neutron_integration>`
+         - Experimental
+         - Missing
+         - Unit
+       * - :ref:`Nova <nova_integration>`
+         - Supported
+         - Minimal
+         - Unit and Integration
+       * - :ref:`Placement <placement_integration>`
+         - Supported
+         - Minimal
+         - Unit and Integration
+
+.. note::
+   Minimal documentation covers only basic configuration and, if available,
+   how to enable notifications.
+
+.. _cinder_integration:
+
+Cinder
+^^^^^^
+The OpenStack Block Storage service integration includes a cluster data
+model collector that creates a in-memory representation of the storage
+resources, strategies that propose solutions based on storage capacity
+and Actions that perform volume migration.
+
+.. _glance_integration:
+
+Glance
+^^^^^^
+The Image service integration is consumed by Nova Helper to create instances
+from images, which was used older releases of Watcher to cold migrate
+instances. This procedure is not used by Watcher anymore and this integration
+is classified as Experimental and may be removed in future releases.
+
+.. _ironic_integration:
+
+Ironic
+^^^^^^
+The Bare Metal service integration includes a data model collector that
+creates an in-memory representation of Ironic resources and Actions that
+allows the management of the power state of nodes. This integration is
+classified as Experimental and may be removed in future releases.
+
+.. _keystone_integration:
+
+Keystone
+^^^^^^^^
+The Identity service integration includes authentication with other services
+and retrieving information about domains, projects and users.
+
+.. _maas_integration:
+
+MAAS (Metal As A Service)
+^^^^^^^^^^^^^^^^^^^^^^^^^
+This integration allows managing bare metal servers of a MAAS service,
+which includes Actions that manage the power state of nodes. This
+integration is classified as Experimental and may be removed in future
+releases.
+
+.. _neutron_integration:
+
+Neutron
+^^^^^^^
+Neutron integration is currently consumed by Nova Helper to create instance,
+which was used by older releases of Watcher to cold migrate instances. This
+procedure is not used by Watcher anymore and this integration is classified
+as Experimental and may be removed in future releases.
+
+.. _nova_integration:
+
+Nova
+^^^^
+Nova service integration includes a cluster data model collector that creates
+an in-memory representation of the compute resources available in the cloud,
+strategies that propose solutions based on available resources and Actions
+that perform instance migrations.
+
+.. _placement_integration:
+
+Placement
+^^^^^^^^^
+Placement integration allows Watcher to track resource provider inventories
+and usages information, building a in-memory representation of those resources
+that can be used by strategies when calculating new solutions.
+