fix: decorator types (#1685)

I found this issue #1667 that had the same errors as me, but the comments didn't help. I also found a different issue nestjs/nest#10959, and the fix they used nestjs/nest#10970, and used that to fix the problem with the InjectMetric decorator.

The problem is that the decorator types are wrong. Record<string, unknown> fails with strict checks, and the key may also be undefined.

Fixes #1667

src/injector.ts

@@ -23,8 +23,8 @@ import { getToken } from "./metrics";
 export function InjectMetric(
   name: string,
 ): (
-  target: Record<string, unknown>,
-  key: string | symbol,
+  target: object,
+  key: string | symbol | undefined,
   index?: number | undefined,
 ) => void {
   const token = getToken(name);