refactor(nestjs): hook up new endpoints

packages/server/src/utils/running-balance.ts

@@ -0,0 +1,15 @@
+
+
+export const runningBalance = (amount: number) => {
+  let runningBalance = amount;
+
+  return {
+    decrement: (decrement: number) => {
+      runningBalance -= decrement;
+    },
+    increment: (increment: number) => {
+      runningBalance += increment;
+    },
+    amount: () => runningBalance,
+  };
+};