fix(api): UserRateLimit schema (#55663)

api/prisma/schema.prisma

@@ -178,9 +178,9 @@ model Donation {
 }
 
 model UserRateLimit {
-  id             String @id @default(auto()) @map("_id") @db.ObjectId
-  /// Field referred in an index, but found no data to define the type.
-  expirationDate Json?
+  id             String  @id @map("_id")
+  counter        Int
+  expirationDate DateTime @db.Date
 
   @@index([expirationDate], map: "expirationDate_1")
 }

api/src/routes/auth.ts

@@ -1,4 +1,5 @@
 import { FastifyPluginCallback, FastifyRequest } from 'fastify';
+// TODO(Post-MVP): use fastify-rate-limit instead of express-rate-limit
 import rateLimit from 'express-rate-limit';
 // @ts-expect-error - no types
 import MongoStoreRL from 'rate-limit-mongo';