[datafeed] set delete-entities=yes is now safer, by checking each entity actually seems deleted. Closes #2165381 Parsers now have to implement the `is_deleted(extid, etype, eid)` method that should return a boolean telling if the given entity exists in the external source or not.

[config, migration] fix https-deny-anonymous option type

[js, i18n] translated strings should use " not ' else they are discarded by xgettext. Closes #1892489