implement new invitation system

* fix comments on the frontend
* move jwt token service to its own module
* other fixes and updates

apps/server/src/core/group/dto/add-group-user.dto.ts

@@ -2,13 +2,9 @@ import { ArrayMaxSize, ArrayMinSize, IsArray, IsUUID } from 'class-validator';
 import { GroupIdDto } from './group-id.dto';
 
 export class AddGroupUserDto extends GroupIdDto {
-  // @IsOptional()
-  // @IsUUID()
-  // userId: string;
-
   @IsArray()
   @ArrayMaxSize(50, {
-    message: 'userIds must an array with no more than 50 elements',
+    message: 'you cannot add more than 50 users at a time',
   })
   @ArrayMinSize(1)
   @IsUUID(4, { each: true })