Add dcmanager peer-group-association management API.
This commit adds peer-group-association APIs of
create/delete/update/show/list/sync,
and adds system-peer API of list subcloud-peer-groups.
Test Plan:
1. PASS - Verify that cloud manage peer-group-association
through api successfully.
2. PASS - Verify that cloud get associated subcloud-peer-group
list with system-peer api successfully.
3. PASS - Check create without providing the must required
parameters.
4. PASS - Check create with wrong peer_group_priority.
5. PASS - Check delete with a not existing association id.
6. PASS - Check system_peer_manager associate peer group,
sync peer group and delete association.
7. PASS - Create an association with 50 subclouds need to
sync. Check the sync status on peer site after
it is synced.
Story: 2010852
Task: 48506
Change-Id: I41c16a8ab13e60f5b1de5b05fbbc51821f7f8d57
Signed-off-by: Zhang Rong(Jon) <rong.zhang@windriver.com>