Revert "Update main.wasp"

This reverts commit ecee41f.

Author: vincanger

app/main.wasp

@@ -96,8 +96,8 @@ app SaaSTemplate {
 entity User {=psl
   id                        Int             @id @default(autoincrement())
   email                     String?         @unique
-  username                  String?         @unique
-  password                  String?
+  username                  String          @unique
+  password                  String
   createdAt                 DateTime        @default(now())
   lastActiveTimestamp       DateTime        @default(now())
   isAdmin                   Boolean         @default(false)