frontend:locale & subscription handling

frontend/src/app.d.ts

@@ -3,12 +3,12 @@
 interface Subscription {
 	id: number | -1;
 	name: string | '';
-	details?: string | '';
-	conditions?: string | '';
-	monthly_fee?: number | -1;
-	hourly_rate?: number | -1;
-	included_hours_per_year?: number | 0;
-	included_hours_per_month?: number | 0;
+	details: string | '';
+	conditions: string | '';
+	monthly_fee: number | 0;
+	hourly_rate: number | 0;
+	included_hours_per_year: number | 0;
+	included_hours_per_month: number | 0;
 }
 
 interface Membership {
@@ -79,6 +79,7 @@ declare global {
 		}
 		interface Types {
 			licenceCategory: LicenceCategory;
+			subscription: Subscription;
 		}
 		// interface PageData {}
 		// interface Platform {}