Addons: allow users to show/hide notifications on latest/non-stable (#11718)
We currently allow users to disable the latest and non-stable
notifications with only one checkbox. This PR split this checkbox into
two, so users can decide to show a notification on latest and/or on
non-stable versions individually.
Note this PR also changes the addons API response:
`non_latest_version_warning` and `external_version_warning` are combined
into `notifications`. I think nobody is using this yet, so I'm not
expecting issues with it. Let me know if you think differently here.
Required by https://github.com/readthedocs/addons/issues/133
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Co-authored-by: Eric Holscher <eric@ericholscher.com>
Co-authored-by: Eric Holscher <25510+ericholscher@users.noreply.github.com>