Add tabbed output support (r8)

Enable HTML tabs in output pages. This is initially for use differentiating virtual
from bare-metal instructions in a consolidated Install doc. Since virtual content is
currently StarlingX-only, content must be conditionalized as in:

.. present tabbed content choice to StarlingX builds

.. only:: virtual

   .. tabs::

      .. tab:: Virtual

         Apples are green, or sometimes red.

      .. tab:: Bare Metal

         .. bare-metal-pear-begin

         Pears are green.

         .. bare-metal-pear-end

.. Present bare-metal only to non-StarlingX builds as non-tabbed content

.. only:: partner

   .. include:: this-file.rst
      :start-after: bare-metal-pear-begin
      :end-before: bare-metal-pear-end

Signed-off-by: Ron Stone <ronald.stone@windriver.com>
Change-Id: Ib65cf59f510e685a82c3d1ab046cb656d0f2fba1

doc/requirements.txt

@@ -2,6 +2,7 @@ sphinx==4.2.0
 openstackdocstheme>=2.2.1,<=2.3.1 # Apache-2.0
 docutils==0.17.1
 PyYAML==6.0
+sphinx-tabs<=3.4.1
 
 # API Reference Guide
 os-api-ref>=1.5.0 # Apache-2.0

doc/source/conf.py

@@ -36,7 +36,8 @@ author = 'StarlingX'
 # ones.
 extensions = [
 #    'openstackdocstheme',
-     'starlingxdocs_plus'
+     'starlingxdocs_plus',
+     'sphinx_tabs.tabs'
 ]
 
 if tags.has('use_spellext'):

tox.ini

@@ -35,7 +35,7 @@ deps =
   -r{toxinidir}/doc/requirements.txt
 commands =
   {[testenv:prebuild-docs]commands}
-  sphinx-build -a -E -W --keep-going -d doc/build/doctrees -t starlingx -t openstack -b html doc/source doc/build/html {posargs}
+  sphinx-build -a -E -W --keep-going -d doc/build/doctrees -t starlingx -t openstack -t virtual -b html doc/source doc/build/html {posargs}
   {[testenv:postbuild-docs]commands}
 # Note: The dev env for the docs team uses a version of tox that does not yet support allowlist_externals
 whitelist_externals = bash