fix(labrinth): tentative billing period update fix (#3722)

* fix(labrinth/billing): add Spain and Singapore to the list of countries for currency inferences

This should fix payments in those countries not going through with their
local currencies for products that do not have USD-only pricing.

* fix(labrinth/billing): tentative fix for subscription periods not updating

Author: AlexTMjugador

apps/labrinth/src/routes/internal/billing.rs

@@ -1020,6 +1020,7 @@ fn infer_currency_code(country: &str) -> String {
         "BE" => "EUR",
         "CY" => "EUR",
         "EE" => "EUR",
+        "ES" => "EUR",
         "FI" => "EUR",
         "FR" => "EUR",
         "DE" => "EUR",
@@ -1066,6 +1067,7 @@ fn infer_currency_code(country: &str) -> String {
         "TW" => "TWD",
         "SA" => "SAR",
         "QA" => "QAR",
+        "SG" => "SGD",
         _ => "USD",
     }
     .to_string()
@@ -1302,6 +1304,12 @@ pub async fn initiate_payment(
             amount: Some(price),
             currency: Some(stripe_currency),
             customer: Some(customer),
+            metadata: interval.map(|interval| {
+                HashMap::from([(
+                    "modrinth_subscription_interval".to_string(),
+                    interval.as_str().to_string(),
+                )])
+            }),
             ..Default::default()
         };