implement `generate-claim-receipt` in API signer service

[roshaans]

.route("/v1/generate-claim-receipt/{account_id}{quest_id}"

1. run internal validate(account_id, quest_id) -> Make this function return true for now.
   • apply validation logic to check for quest completion -> you can create a dummy function for now. We will create more tasks to add graphql-client logic later
2. return signed(hash) as a receipt to client or send a error message if quest not complete -> call the internal signMessage on the payload the user sends in and return it.