use pagination for keycloak_group_memberships resource (#527)

docs/resources/group_memberships.md

@@ -16,7 +16,9 @@ Also note that you should not use `keycloak_group_memberships` with a group has
 This resource **should not** be used to control membership of a group that has its members federated from an external
 source via group mapping.
 
-To non-exclusivly manage the group's of a user, see the [`keycloak_user_groups` resource][1]
+To non-exclusively manage the group's of a user, see the [`keycloak_user_groups` resource][1]
+
+This resource paginates its data loading on refresh by 50 items.
 
 ## Example Usage
 

keycloak/group.go

@@ -207,10 +207,17 @@ func (keycloakClient *KeycloakClient) ListGroupsWithName(realmId, name string) (
 
 func (keycloakClient *KeycloakClient) GetGroupMembers(realmId, groupId string) ([]*User, error) {
 	var users []*User
+	var first, pagination int = 0, 50
+	var iterationUsers []*User
 
-	err := keycloakClient.get(fmt.Sprintf("/realms/%s/groups/%s/members?max=-1", realmId, groupId), &users, nil)
-	if err != nil {
-		return nil, err
+	for ok := true; ok; ok = (len(iterationUsers) > 0) {
+		iterationUsers = nil
+		err := keycloakClient.get(fmt.Sprintf("/realms/%s/groups/%s/members?max=%d&first=%d", realmId, groupId, pagination, first), &iterationUsers, nil)
+		if err != nil {
+			return nil, err
+		}
+		users = append(users, iterationUsers...)
+		first += pagination
 	}
 
 	for _, user := range users {