Fix type check of unsupported language codes in Stripe checkout session

apps/api/src/app/subscription/subscription.service.ts

@@ -23,8 +23,6 @@ import { addMilliseconds, isBefore } from 'date-fns';
 import ms, { StringValue } from 'ms';
 import Stripe from 'stripe';
 
-import { StringLiteral } from './types/string-literal.type';
-
 @Injectable()
 export class SubscriptionService {
   private readonly logger = new Logger(SubscriptionService.name);
@@ -270,7 +268,11 @@ export class SubscriptionService {
     const unsupportedLanguageCodes: Record<
       Exclude<
         (typeof SUPPORTED_LANGUAGE_CODES)[number],
-        StringLiteral<Stripe.Checkout.SessionCreateParams.Locale>
+        // Extract removes OtherString of Stripe, which matches every string
+        Extract<
+          Stripe.Checkout.SessionCreateParams.Locale,
+          (typeof SUPPORTED_LANGUAGE_CODES)[number]
+        >
       >,
       true
     > = {

apps/api/src/app/subscription/types/string-literal.type.ts

@@ -1,7 +0,0 @@
-// Removes the open string type (e.g. OtherString of Stripe), which matches
-// every string, and keeps only the string literals
-export type StringLiteral<T> = T extends string
-  ? string extends T
-    ? never
-    : T
-  : never;