Move download counting to worker (#306)

* Move download counting to worker

* Run `cargo sqlx prepare`

* Format & some Clippy fixes

src/util/guards.rs

@@ -0,0 +1,12 @@
+use actix_web::guard::GuardContext;
+
+pub const ADMIN_KEY_HEADER: &str = "Modrinth-Admin";
+pub fn admin_key_guard(ctx: &GuardContext) -> bool {
+    let admin_key = std::env::var("LABRINTH_ADMIN_KEY")
+        .expect("No admin key provided, this should have been caught by check_env_vars");
+
+    ctx.head()
+        .headers()
+        .get(ADMIN_KEY_HEADER)
+        .map_or(false, |it| it.as_bytes() == admin_key.as_bytes())
+}

src/util/mod.rs

@@ -1,6 +1,7 @@
 pub mod auth;
 pub mod env;
 pub mod ext;
+pub mod guards;
 pub mod routes;
 pub mod validate;
 pub mod webhook;