refactor: extract api implementation to package

Extracts the API implementation to a package so we can
potentially reuse it across different applications in the
event that we move off using a Next.js API route.

Additionally tidies up the tokens page and form to be more simplified.

packages/api/v1/middleware/authenticated.ts

@@ -0,0 +1,37 @@
+import type { NextApiRequest } from 'next';
+
+import { getUserByApiToken } from '@documenso/lib/server-only/public-api/get-user-by-token';
+import type { User } from '@documenso/prisma/client';
+
+export const authenticatedMiddleware = <
+  T extends {
+    req: NextApiRequest;
+  },
+  R extends {
+    status: number;
+    body: unknown;
+  },
+>(
+  handler: (args: T, user: User) => Promise<R>,
+) => {
+  return async (args: T) => {
+    try {
+      const { authorization: token } = args.req.headers;
+
+      if (!token) {
+        throw new Error('Token was not provided for authenticated middleware');
+      }
+
+      const user = await getUserByApiToken({ token });
+
+      return await handler(args, user);
+    } catch (_err) {
+      return {
+        status: 401,
+        body: {
+          message: 'Unauthorized',
+        },
+      } as const;
+    }
+  };
+};