Lsh/team management compatibility (#113)

* Add roleName in SysUser class, for directly use;
Add "managable" variable in SysTeam class, for team management page to upload;

* Fix: ADMIN can get all SysTeam record;
Set manageable = false for newly created object;

* Default team cannot be deleted.
Optimize user existence check when the only member is the requestor to delete the team.

* Default team cannot be deleted.
Optimize user existence check when the only member is the requestor to delete the team.

* Create a new API as the old API is used in other place and hence it's targeting function should not be modified.

* - Modify /userTeam/addRelation API, use mailAddress instead of userId as input;
- Optimize logic of setting SysTeam list manageable attribute;
- Modify /userTeam/queryUsers API:
  - Add manageable attribute;
  - Remove Default team member when requestor's ROLE is USER;
  - Set manageable = true for only the requestor when requestor's ROLE is USER;

* Modify /queryUsers API

* NPE check for teamAdmin set

center/src/main/java/com/microsoft/hydralab/center/service/UserTeamManagementService.java

@@ -121,14 +121,16 @@ public List<SysUser> queryUsersByTeam(String teamId) {
     public List<SysUser> queryTeamUsersWithTeamAdmin(String teamId) {
         List<SysUser> allUsers = queryUsersByTeam(teamId);
         Set<String> teamAdminSet = teamAdminListMap.get(teamId);
-        allUsers.forEach(user -> {
-            if (teamAdminSet.contains(user.getMailAddress())) {
-                user.setTeamAdmin(true);
-            }
-            else {
-                user.setTeamAdmin(false);
-            }
-        });
+        if (!CollectionUtils.isEmpty(teamAdminSet)) {
+            allUsers.forEach(user -> {
+                if (teamAdminSet.contains(user.getMailAddress())) {
+                    user.setTeamAdmin(true);
+                }
+                else {
+                    user.setTeamAdmin(false);
+                }
+            });
+        }
 
         return allUsers;
     }