Use i32 for database IDs since that's support for postgres too

rc_database/src/schema/user.rs

@@ -4,7 +4,7 @@ use sea_orm::entity::prelude::*;
 #[sea_orm(table_name = "users")]
 pub struct Model {
     #[sea_orm(primary_key)]
-    pub id: u32,
+    pub id: i32,
     pub creation_time: i64, // seconds since unix epoch
     pub public_id: String,
     pub display_name: String,