feat(labrinth): database seed data fixtures for better installation and testing (#4132)

* feat(labrinth): database seed data fixtures for better installation and testing

* chore(labrinth): simplify and fixup seed data fixture

* docs(contributing/labrinth): enable all useful features for `sqlx-cli` install

* chore(docs/labrinth): fix typo

* chore(docs/labrinth): fix `cargo fmt` parameter typo

* chore: replace Labrinth -> labrinth

apps/labrinth/tests/common/dummy_data.rs

@@ -292,7 +292,7 @@ pub async fn add_dummy_data(api: &ApiV3, db: TemporaryDatabase) -> DummyData {
     let pool = &db.pool.clone();
 
     pool.execute(
-        include_str!("../files/dummy_data.sql")
+        include_str!("../fixtures/dummy_data.sql")
             .replace("$1", &Scopes::all().bits().to_string())
             .as_str(),
     )