To add metadata to a group, send the metadata object inside the group object while creating a group. The same metadata object will be received in group list API with group object. The metadata object is a map with string keys and values.
Sample Group Object JSON with Metadata:
{
"clientGroupId":"Client Group Id",
"groupName" : "Group Name",
"groupMemberList" : ["UserName1", "UserName2", "UserName3"],
"imageUrl": "Group image Url",
"metadata" : {
"key1" : "value1",
"key2" : "value2"
}
}