Add docs key and point at Discourse

Add the 'docs' key and point it at a Discourse topic
previously populated with the charm's README contents.

When the new charm revision is released to the Charmhub,
this Discourse-based content will be displayed there. In
the absense of the this new key, the Charmhub's default
behaviour is to display the value of the charm's
'description' key.

Change-Id: I0fb5e14bd2e58d4abdcce6e230d5c4c1a1d00af7
(cherry picked from commit af700cf326)

metadata.yaml

@@ -21,6 +21,7 @@ description: |
   .
   This charm provides the Ceph OSD personality for expanding storage capacity
   within a ceph deployment.
+docs: https://discourse.charmhub.io/t/ceph-osd-docs-index/10545
 extra-bindings:
   public:
   cluster:

test-requirements.txt

@@ -44,3 +44,6 @@ croniter            # needed for charm-rabbitmq-server unit tests
 pyparsing<3.0.0  # aodhclient is pinned in zaza and needs pyparsing < 3.0.0, but cffi also needs it, so pin here.
 cffi==1.14.6; python_version < '3.6'  # cffi 1.15.0 drops support for py35.
 pyopenssl<=22.0.0
+
+# newer jsonschema needs rustc and cargo
+jsonschema<4.18.0

tox.ini

@@ -80,9 +80,7 @@ deps = -r{toxinidir}/requirements.txt
 [testenv:pep8]
 basepython = python3
 deps = flake8==3.9.2
-       charm-tools==2.8.4
 commands = flake8 {posargs} hooks unit_tests tests actions lib files
-           charm-proof
 
 [testenv:cover]
 # Technique based heavily upon