The shard follow task cleaner executes on behalf of the user to clean up
a shard follow task after the follower index has been
deleted. Otherwise, these persistent tasks are left laying around, and
they fail to execute because the follower index has been deleted. In the
face of security, attempts to complete these persistent tasks would
fail. This is because these cleanups are executed under the system
context (this makes sense, they are happening on behalf of the user
after the user has executed an action) but the system role was never
granted the permission for persistent task completion. This commit
addresses this by adding this cluster privilege to the system role.
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.
Renamed the follow qa modules:
`multi-cluster-downgraded-to-basic-license` to `downgraded-to-basic-license`
`multi-cluster-with-non-compliant-license` to `non-compliant-license`
`multi-cluster-with-security` to `security`
Moved the `chain` module into the `multi-cluster` module and
changed the `multi-cluster` to start 3 clusters.
Followup from #36031
Jason Tedor
Martijn van Groningen