There are potential use-cases for allowing the flagging of config entities.
In the message_subscribe module, flags are used to denote subscriptions:
This screenshot from the original IS isn't from message_subscribe, but indicates the same use case:
where announcements and discussions are flagged node types.
Utilize the
Dynamic Entity Reference →
module for the flagging entity's reference column (now a single flagged_entity base field.)
$fields['flagged_entity'] = BaseFieldDefinition::create('dynamic_entity_reference')
->setLabel(t('Flagged entity'))
->setDescription(t('The entity that has been flagged.'))
->setCardinality(1)
->setRequired(TRUE);
This replaces the previous 3 base fields on the flagging entity (entity_type, entity_id, and the computed flagged_entity).
Needs review
4.0
Flag core
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
And it looks like some additional tweaks are necessary if you're using DER 3.x.
Looks like I missed something for the DER 3.x version.