refactor: created custom error for a token already exists

src/models/token.ts

@@ -1,5 +1,6 @@
 import { eq, or, sql } from "drizzle-orm";
 
+import { TokenAlreadyExistsError } from "~/libs/errors/TokenAlreadyExists";
 import type { Env } from "~/types/env";
 
 import { getDb } from "./db";
@@ -34,7 +35,7 @@ export function saveToken(
         !existingToken.username &&
         !username
       ) {
-        throw new Error("Token already exists in the database");
+        throw new TokenAlreadyExistsError();
       }
 
       return updateToken(env, deviceId, token, username);