firebase-admin-node: Firebase appcheck token verification fails because the sdk can't retrieve JWKS

Step 2: Describe your environment

• Operating System version: macos ventura 13.4
• Firebase SDK version: 11.10.1
• Firebase Product: appcheck
• Node.js version: 16
• NPM version: 8.18

Step 3: Describe the problem

When the sdk trys to fetch the jwks from google https://firebaseappcheck.googleapis.com/v1/jwks to verify the appcheck token it errors because the endpoint is returning 403 forbidden. It seems that google has added this rate limit for non authenticated identities lately. It can only be bypassed by passing a X-goog-api-key. In the sdk code for appcheck there is no api key passed nor is there the ability to pass an api key as an enduser.

ERROR:

Error: Error fetching Json Web Keys: Forbidden
    at AppCheckTokenVerifier.mapJwtErrorToAppCheckError (/opt/nodejs/node_modules/firebase-admin/lib/app-check/token-verifier.js:144:16)
    at /opt/nodejs/node_modules/firebase-admin/lib/app-check/token-verifier.js:119:24
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async Runtime.handler (webpack:///./src/functions/authorization/appcheck/index.ts?:39:13)

I double checked and ran a couple of requests in postman against the jwks endpoint and received a forbidden error as well after some time.

Steps to reproduce:

1. setup firebase admin sdk
2. try to verify multiple appcheck tokens

Relevant Code:

const appCheckVerification = async (req, res, next) => {
    const appCheckToken = req.header("X-Firebase-AppCheck");

    if (!appCheckToken) {
        res.status(401);
        return next("Unauthorized");
    }

    try {
        const appCheckClaims = await getAppCheck().verifyToken(appCheckToken); !!!FAILS HERE!!!

        // If verifyToken() succeeds, continue with the next middleware
        // function in the stack.
        return next();
    } catch (err) {
        res.status(401);
        return next("Unauthorized");
    }
}

Using the sdk to verify an appcheck token does not work after hitting the rate limit of the jwks endpoint. It seems like an api key header needs to be passed in this line: https://github.com/firebase/firebase-admin-node/blob/a4019e491c9d36167853eaba056adebd0e9dfc87/src/utils/jwt.ts#L61