Prevent removing participants with expenses

src/lib/api.ts

@@ -66,6 +66,18 @@ export async function deleteExpense(expenseId: string) {
   })
 }
 
+export async function getGroupExpensesParticipants(groupId: string) {
+  const expenses = await getGroupExpenses(groupId)
+  return Array.from(
+    new Set(
+      expenses.flatMap((e) => [
+        e.paidById,
+        ...e.paidFor.map((pf) => pf.participantId),
+      ]),
+    ),
+  )
+}
+
 export async function updateExpense(
   groupId: string,
   expenseId: string,