Add tag for tempest plugins

This commit adds a new deliverable type tag to describe tempest
plugins. For right now this is just for standalone plugin repos.
However the vast majority of tempest plugins are packaged in the
project repos. This is actually an anti-pattern and makes consuming
it more difficult. [1] But, cleaning that up is a separate matter. In
the interim it might be worth adding the tag to those repos with
included plugins as well. But that is a separate discussion to have
and will happen in, a follow on change.

[1] http://docs.openstack.org/developer/tempest/plugin.html#standalone-plugin-vs-in-repo-plugin

Change-Id: Ia713945e88f9f207f9a260eb83b9e595629c4bc3

reference/projects.yaml

@@ -405,6 +405,7 @@ designate:
       tags:
         - release:independent
         - type:library
+        - type:tempest-plugin
     python-designateclient:
       repos:
         - openstack/python-designateclient
@@ -824,6 +825,7 @@ horizon:
       tags:
         - type:library
         - release:independent
+        - type:tempest-plugin
     xstatic-angular:
       repos:
         - openstack/xstatic-angular
@@ -5810,6 +5812,7 @@ sahara:
       tags:
         - release:independent
         - type:library
+        - type:tempest-plugin
     sahara-specs:
       repos:
         - openstack/sahara-specs

reference/tags/index.rst

@@ -47,6 +47,7 @@ Release Management Tags
    type_horizon-plugin
    type_library
    type_service
+   type_tempest-plugin
 
 Vulnerability Management Tags
 =============================

reference/tags/type_tempest-plugin.rst

@@ -0,0 +1,56 @@
+::
+
+  This work is licensed under a Creative Commons Attribution 3.0
+  Unported License.
+  http://creativecommons.org/licenses/by/3.0/legalcode
+
+.. _`tag-type:tempest-plugin`:
+
+=====================
+ type:tempest-plugin
+=====================
+
+This tag is part of the type-classification system for projects
+managed by the release team. ``type:tempest-plugin`` indicates that a
+deliverable is meant to be consumed by :ref:`project-tempest` as a
+plug-in, to provide an unified integration test suite for a given project.
+
+
+Application to current projects
+===============================
+
+.. tagged-projects:: type:tempest-plugin
+
+
+Rationale
+=========
+
+We have a growing number of projects that are Tempest plugins, and it would be
+useful to have them easily grouped together. Using this tag will help both users
+and automated tooling identify which deliverables provide companion
+functionality for Tempest.
+
+
+Requirements
+============
+
+* The repository contains code meant to be dynamically loaded by
+  Tempest to provide an unified integration test suite for a given project.
+
+
+Tag application process
+=======================
+
+Anyone may propose adding or removing this tag to a set of projects by
+proposing a change to the openstack/governance repository. The change
+is reviewed by the Release Team and the QA PTL, and the Technical
+Committee finally approves it using its lazy consensus approval rule.
+
+
+Deprecation
+===========
+
+There is no deprecation process for tags in the ``type`` namespace. If
+we need to change the type of a project, we can just do that.
+
+.. _releases.openstack.org: http://releases.openstack.org/