add check username query

backend/src/auth/INALIENABLE_RIGHTS.ts

@@ -8,4 +8,5 @@ export const INALIENABLE_RIGHTS = [
   RIGHTS.SET_PASSWORD,
   RIGHTS.QUERY_TRANSACTION_LINK,
   RIGHTS.QUERY_OPT_IN,
+  RIGHTS.CHECK_USERNAME,
 ]

backend/src/auth/RIGHTS.ts

@@ -34,6 +34,7 @@ export enum RIGHTS {
   LIST_ALL_CONTRIBUTION_MESSAGES = 'LIST_ALL_CONTRIBUTION_MESSAGES',
   OPEN_CREATIONS = 'OPEN_CREATIONS',
   USER = 'USER',
+  CHECK_USERNAME = 'CHECK_USERNAME',
   // Admin
   SEARCH_USERS = 'SEARCH_USERS',
   SET_USER_ROLE = 'SET_USER_ROLE',

backend/src/graphql/resolver/UserResolver.ts

@@ -498,6 +498,17 @@ export class UserResolver {
     return true
   }
 
+  @Authorized([RIGHTS.CHECK_USERNAME])
+  @Query(() => Boolean)
+  async checkUsername(@Arg('username') username: string): Promise<boolean> {
+    try {
+      await validateAlias(username)
+      return true
+    } catch {
+      return false
+    }
+  }
+
   @Authorized([RIGHTS.UPDATE_USER_INFOS])
   @Mutation(() => Boolean)
   async updateUserInfos(