Sphinx/ReadTheDocs supports automatically translating links written as
to `.md` files to point to the corresponding `.html` files, so this
migration does not change the resulting HTML output in ReadTheDocs.
But it does fix apparent broken links on GitHub.
This doesn't prevent people from reading the documentation on GitHub
(so doesn't mitigate the fact that some rtd-specific syntax does not
render properly on GH), but it will prevent us from getting erroneous
issues reported about the hyperlinks not working.
Fixes: #11087.
This is required in some AWS regions.
The right long-term fix is to move to boto3 which doesn't have this
problem.
Allows us to downgrade the priority of #9376.
This moves the documentation for this feature out of
prod_settings_template.py, so that we can edit it more easily.
We also add a bucket policy, which is part of what one would want to
use this in production.
This addresses much, but not all, of #9361.