These are now returning the correct canonical URL (thanks to a Cloudflare worker script), and letting search engines spider them again will hopefully boost visibility of that canonical URL.
Regardless of how the top-level StreamBlock is instantiated, or what its required Meta attribute says at that point, the StreamField's blank kwarg (defaulting to False) should be the sole indicator of whether the field is required or not.
Fixes #5983; possibly also has a bearing on #4306. A CSS rule dating from the original StreamField design was hiding the 'required' asterisk on fields within a required StreamField, presumably on the mistaken belief that they duplicate the information given by the top-level asterisk on the streamfield. (In #5983 this was reported as a regression in 2.7 when the react-streamfield CSS was introduced, so it's possible that the old design had something to mitigate this, e.g. an asterisk being inserted elsewhere.)
This fixes #6393 by modifying the constraint to use an IN condition
which supports both Postgres and SQL Server. Previously, the `|` (OR)
condition was only supported by Postgres because SQL Server only
supports AND conditions.
The implementation follows suggestions from @gasman in
https://github.com/wagtail/wagtail/issues/6393#issuecomment-732161057:
* Migration 0050 is modified to not break on SQL Server
* Added migration 0060 to add or replace the constraint
Additionally, this allows for and documents a `DATABASE_DRIVER` env
variable to be set for testing, to allow a different SQL Server driver
(e.g. FreeTDS on Mac/Linux); and adds the specific `host_is_server`
option for FreeTDS (won't affect SQL Server Native Client on CI).
Facebook and Instagram embeds configuration section should include the default finders for all other providers. It's unclear for someone who just wants to fix his facebook embeds
