DOC-11383 clarify collection_access for channel assignment

[torcolvin]

DOC-11383 clarify collection_access for channel assignment

This is really just a scaffold for @simon-dew to improve upon. This should pick up changes in couchbase/sync_gateway#7473 and rebuild redocly and preferably also static api doc changes.

The gist is that toplevel admin_channels is present for the _default._default collection for backward compatibility and a GET will show admin_channels in the toplevel. For a PUT:

"collection_access": {
	"_default": {
    	"_default": {
        	"admin_channels": ["Channel1","Channel3","RandomChannel"]
          }
    }
}

or

"admin_channels": ["Channel1","Channel3","RandomChannel"]

are equivalent.

I think this is out of scope for this ticket, but I think dropping the old file based pre 3.x configuration might be warranted. Note, collection_access is only available on 3.1+ since 3.1 is the first version that supports collections. However, 3.0 has been out of full maintenance since October 2023.

Note: these links are broken <.> Here we have added the channels _channel2_, _channel3_ and _SkyChannel_ to the role _Edge2_ {configuration-schema-database--pfx--db}-roles-this_role-admin_channels[databases.$db.users.$user.$collection_access.$scopename.$collectionname.$admin_channels] because regenerating the json schemas is probably broken. However, the old links were broken as well.

I don't expect this to be the final copy, and will leave it up to Simon to finish this PR and address any copy changes he wants.

[simon-dew]

Note: these links are broken <.> Here we have added the channels _channel2_, _channel3_ and _SkyChannel_ to the role _Edge2_ {configuration-schema-database--pfx--db}-roles-this_role-admin_channels[databases.$db.users.$user.$collection_access.$scopename.$collectionname.$admin_channels] because regenerating the json schemas is probably broken.

I think these links are broken because the users key is not documented:

users: (unknown),

And I think that is probably related to DOC-12510, which is currently with @osfameron .

[simon-dew]

TBH I'm happy just to merge this for now and address the main points of the ticket. The broken config file links at least take the user to the correct page, if not the correct spot within the page. Fixing those links can be devolved onto DOC-12510.

[simon-dew]

LGTM (with modifications). Thanks!