change creationDate in sendCoinArgs to String

backend/src/federation/client/1_0/model/SendCoinsArgs.ts

@@ -9,8 +9,8 @@ export class SendCoinsArgs {
   @Field(() => String)
   userReceiverIdentifier: string
 
-  @Field(() => Date)
-  creationDate: Date
+  @Field(() => String)
+  creationDate: string
 
   @Field(() => Decimal)
   amount: Decimal

backend/src/federation/client/1_0/query/voteForSendCoins.ts

@@ -4,7 +4,7 @@ export const voteForSendCoins = gql`
   mutation (
     $communityReceiverIdentifier: String!
     $userReceiverIdentifier: String!
-    $creationDate: Date!
+    $creationDate: String!
     $amount: Decimal!
     $memo: String!
     $communitySenderIdentifier: String!

backend/src/graphql/resolver/util/processXComSendCoins.ts

@@ -42,7 +42,7 @@ export async function processXComSendCoins(
         ? receiverCom.communityUuid
         : CONFIG.FEDERATION_XCOM_RECEIVER_COMMUNITY_UUID
       args.userReceiverIdentifier = recipient.gradidoID
-      args.creationDate = creationDate
+      args.creationDate = creationDate.toISOString()
       args.amount = amount
       args.memo = memo
       args.communitySenderIdentifier = senderCom.communityUuid