[FR] Add check to verify if auth emulator host is valid

[amalej]

Is your feature request related to a problem? Please describe.
I accidentally used http://127.0.0.1:9099 instead of 127.0.0.1:9099 when setting FIREBASE_AUTH_EMULATOR_HOST.

Even though the emulator thew an error like below, it still took me a while to figure out what I did wrong 🤦 :

FirebaseAppError: Error while making request: getaddrinfo ENOTFOUND http. Error code: ENOTFOUND
    at C:\Users\PATH\firebase-admin-node\lib\utils\api-request.js:268:19
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async main (file:///C:/Users/PATH/auth.js:12:5) {
  errorInfo: {
    code: 'app/network-error',
    message: 'Error while making request: getaddrinfo ENOTFOUND http. Error code: ENOTFOUND'
  },
  codePrefix: 'app'
}

Describe the solution you'd like
Throw an error message indicating that http and https should not be included when setting FIREBASE_AUTH_EMULATOR_HOST. Found a similar logic in

firebase-admin-node/src/storage/storage.ts

Lines 51 to 56 in a46086b

	if (firebaseStorageEmulatorHost.match(/https?:\/\//)) {
	throw new FirebaseError({
	code: 'storage/invalid-emulator-host',
	message: 'FIREBASE_STORAGE_EMULATOR_HOST should not contain a protocol (http or https).',
	});
	}

Describe alternatives you've considered
N/A

Additional context
N/A

[google-oss-bot]

I found a few problems with this issue:

• I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.
• This issue does not seem to follow the issue template. Make sure you provide all the required information.