Fixed #22310 -- Documented exact usage of SECRET_KEY

Thanks to Tim Graham for the review.
Made minor typographic correction to SECRET_KEY docs.

4ad57bbe31bc1813264824111de2f9f74dbda0d6 included a few odd
quotation marks.
Fix formatting error in UUIDField docs.
Fixed comment typo in django/template/__init__.py
Improved AppRegistryNotReady message.
Revert "Improved AppRegistryNotReady message."

This reverts commit 6fa9fa91a5fcb228b3c385b35a2018b3821a447a.

Aymeric: "I chose not to talk about django.setup() here on purpose.
This will hardly always be the correct solution."
Fixed #22064 -- Add check for related_name

Validates that related_name is a valid Python id or ends with a '+' and
it's not a keyword. Without a check it passed silently leading to
unpredictable problems.

Thanks Konrad Świat for the initial work.
Updated assertQuerysetEqual documentation following 311b3ad9db94c3e04f929c2622be4f10d759f45e
Merge pull request #3312 from tchaumeny/doc_assert_queryset

Updated assertQuerysetEqual documentation following 311b3ad9db94
Fixed #23597 -- Clarified the manager that {Single,Multiple}ObjectMixin.model uses.
Fixed #23604 -- Allowed related m2m fields to be references in the admin.

Thanks Simon Charette for review.
Fixed #23601 -- Ensured view exists in URLconf before importing it in admindocs.
Updated links in admin docs to use :ref:

per Sphinx docs: "Using ref is advised over standard reStructuredText
links to sections because it works across files, when section headings
are changed, and for all builders that support cross-references.
Added my bio to the core team.
Fixed #23594 -- Fixed deepcopy on ErrorList.

Thanks Troy Grosfield for the report and Tim Graham for the tests.
Fixed #23602 -- Add comment on get_absolute_url regarding user input
Merge pull request #3307 from Markush2010/ticket23602

Fixed #23602 -- Add comment on get_absolute_url regarding user input
Moved release note for refs #23601 to 1.7.1.
Merge pull request #3308 from aericson/ticket_22064

Fixed #22064 -- Add check for related_name
Fixed #23593 -- Fixed crash in AdminEmailHandler with non-ASCII characters in request.

Thanks edevil for the report and Simon Charette for review.