This commit introduces the forget follower API. This API is needed in cases that
unfollowing a following index fails to remove the shard history retention leases
on the leader index. This can happen explicitly through user action, or
implicitly through an index managed by ILM. When this occurs, history will be
retained longer than necessary. While the retention lease will eventually
expire, it can be expensive to allow history to persist for that long, and also
prevent ILM from performing actions like shrink on the leader index. As such, we
introduce an API to allow for manual removal of the shard history retention
leases in this case.
This commit modifies the put follow index action to use a
CcrRepository when creating a follower index. It routes
the logic through the snapshot/restore process. A
wait_for_active_shards parameter can be used to configure
how long to wait before returning the response.
* Moved `AcknowledgedResponse` to core package
* Made AcknowledgedResponse not abstract and provided a default parser,
so that in cases when the field name is not overwritten then there
is no need for a subclass.
Relates to #33824
Jason Tedor
Martijn van Groningen
Tim Brooks