Link to (some) plugin doc pages

We would like to use autoprogram-cliff to generate full docs inline for
each plugin. But for the following projects, that breaks the build:

- octavia
- rsd
- trove
- watcher
- zun

For those projects, we're using list-plugins instead, because that
builds, and it's better than nothing; but it only provides summaries of
the commands.

So with this commit, we add a link to the plugin documentation from the
actual plugin project where such documentation exists, which currently
is just:

- octavia
- watcher
- zun

(For rsd, I couldn't find openstack-published docs at all; for trove,
published docs exist, but the osc plugin isn't documented.)

Change-Id: I7c826ecef4319bead239e11b5f975302b2f24d1b
Story: #1735016
Task: #37244

doc/source/cli/plugin-commands/octavia.rst

@@ -3,5 +3,8 @@ octavia
 
 .. TODO(efried): cut over to autoprogram-cliff once doc build is fixed
 
+For more details, see the :python-octaviaclient-doc:`python-octaviaclient
+plugin documentation </cli/index>`.
+
 .. list-plugins:: openstack.load_balancer.v2
    :detailed:

doc/source/cli/plugin-commands/watcher.rst

@@ -3,5 +3,8 @@ watcher
 
 .. TODO(efried): cut over to autoprogram-cliff once doc build is fixed
 
+For more details, see the :python-watcherclient-doc:`python-watcherclient
+plugin documentation </cli/openstack_cli>`.
+
 .. list-plugins:: openstack.infra_optim.v1
    :detailed:

doc/source/cli/plugin-commands/zun.rst

@@ -3,5 +3,8 @@ zun
 
 .. TODO(efried): cut over to autoprogram-cliff once doc build is fixed
 
+For more details, see the :python-zunclient-doc:`python-zunclient plugin
+documentation </cli/command-list>`.
+
 .. list-plugins:: openstack.container.v1
    :detailed:

doc/source/conf.py

@@ -34,6 +34,12 @@ extensions = ['sphinx.ext.autodoc',
 repository_name = 'openstack/python-openstackclient'
 use_storyboard = True
 
+openstack_projects = [
+    'python-octaviaclient',
+    'python-watcherclient',
+    'python-zunclient',
+]
+
 # Add any paths that contain templates here, relative to this directory.
 #templates_path = ['_templates']