[Backport 2.x] [Refactor] Metadata members from ImmutableOpenMap to j.u.Map (#7165)#8241

Merged

nknize merged 3 commits intoopensearch-project:2.xfrom nknize:backport/backport-7165-to-2.x

Jun 26, 2023

+641-804

Commits on Jun 23, 2023

[Refactor] ClusterInfo to use j.util.Map instead of ImmutableOpenMap (opensearch-project#7126 )
nknize
committed
[Refactor] Metadata members from ImmutableOpenMap to j.u.Map (opensearch-project#7165 )
nknize
committed
merge cleanup
nknize
committed