refactor: combine models and db crate together

crates/core/database/examples/migrate.rs

@@ -0,0 +1,8 @@
+use revolt_database::DatabaseInfo;
+use revolt_models::*;
+
+#[async_std::main]
+async fn main() {
+    let db = Database(DatabaseInfo::Auto.connect().await.unwrap());
+    db.migrate_database().await.unwrap();
+}