docs: add automatically generated list of cfg opts

This change will include an automatically generated list of
config options in the cloudbase-init docs.

It's useful as some config options are not currently mentioned in
the docs and it's also nice to be able to have a quick overview
of all available options without having to go through the code.
You can also send links to certain config options or groups.

Note that long config opt lines are not wrapped and look quite bad,
especially with the current theme (may consider switching to some
other theme, maybe the "alabaster" one included by default by
sphinx). Still better than not having this at all though.

We're also adding the zuul jobs that validate release notes and
docs, required for testing this patch.

Change-Id: Ibaff3a91e7f1345aaaac0c29b995e7c25b9e4669

.zuul.yaml

@@ -1,4 +1,12 @@
 - project:
+    check:
+      jobs:
+        - build-openstack-releasenotes
+        - build-openstack-sphinx-docs
+    gate:
+      jobs:
+        - build-openstack-releasenotes
+        - build-openstack-sphinx-docs
     post:
       jobs:
         - cbsl-init-upload-git-mirror

doc/source/conf.py

@@ -32,6 +32,8 @@ import shlex
 extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.viewcode',
+    'oslo_config.sphinxext'
+
 ]
 
 # Add any paths that contain templates here, relative to this directory.

doc/source/config.rst

@@ -0,0 +1,13 @@
+.. _config_list:
+
+===============================
+Configuration options reference
+===============================
+
+The following is an overview of all available configuration options in
+cloudbase-init.
+
+.. show-options::
+
+    cloudbaseinit.conf
+    oslo.log

doc/source/index.rst

@@ -16,6 +16,7 @@ Contents:
    services
    plugins
    userdata
+   config
 
 
 Indices and tables

doc/source/tutorial.rst

@@ -93,6 +93,7 @@ initialization cases.
 More of these explained options are available under the :ref:`services`,
 :ref:`plugins` and :ref:`userdata` documentation.
 
+A complete list of config options can be found at :ref:`config_list`.
 
 .. _execution: