feat(api): allow unauthed requests to /systems/:id/settings

crates/api/src/auth.rs

@@ -1,3 +1,5 @@
+use pluralkit_models::{PKSystem, PrivacyLevel, SystemId};
+
 pub const INTERNAL_SYSTEMID_HEADER: &'static str = "x-pluralkit-systemid";
 pub const INTERNAL_APPID_HEADER: &'static str = "x-pluralkit-appid";
 
@@ -19,4 +21,28 @@ impl AuthState {
     pub fn app_id(&self) -> Option<i32> {
         self.app_id
     }
+
+    pub fn access_level_for(&self, a: &impl Authable) -> PrivacyLevel {
+        if self
+            .system_id
+            .map(|id| id == a.authable_system_id())
+            .unwrap_or(false)
+        {
+            PrivacyLevel::Private
+        } else {
+            PrivacyLevel::Public
+        }
+    }
+}
+
+// authable trait/impls
+
+pub trait Authable {
+    fn authable_system_id(&self) -> SystemId;
+}
+
+impl Authable for PKSystem {
+    fn authable_system_id(&self) -> SystemId {
+        self.id
+    }
 }