Currently, both the NativeUsersStore and NativeRolesStore can undergo
multiple state transitions. This is done primarily to check if the
security index is usable before it proceeds. However, such checks are
only needed for the tests, because if the security index is unavailable
when it is needed, the downstream actions invoked by the
NativeUsersStore and NativeRolesStore will throw the appropriate
exceptions notifying of that condition. In addition, both the
NativeUsersStore and NativeRolesStore had much duplicate code that
listened for cluster state changes and made the exact same state
transitions.
This commit removes the complicated state transitions in both classes
and enables both classes to use the SecurityTemplateService to monitor
all of the security index lifecycle changes they need to be aware of.
This commit also moves the logic for determining if the security index
needs template and/or mapping updates to the SecurityLifecycleService,
and makes the NativeRealmMigrator solely responsible for applying the
updates.
Original commit: elastic/x-pack-elasticsearch@b31d144597
4a001706e7