Firestore REST API make authenticated request with http-client - rest

Question

I want to get data from a firestore via the REST API. I'm using an HTTP-Client (Webstorm) and do the following.
First I authenticate with Google which works fine and does return a token:
POST https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword?key=<firebase-api-key>
Accept: application/json
Content-Type: application/json
{
"email": "some#email.com",
"password": "notthispassword"
}
But then, trying to get data from the firestore (not realtime-db) like this
GET https://firestore.googleapis.com/v1/projects/<projectId>/databases/(default)/documents/<collection>
Accept: application/json
Authorization: Bearer <token from auth response>
it keeps telling me:
{
"error": {
"code": 401,
"message": "Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
"status": "UNAUTHENTICATED"
}
}
These are my firestore security rules:
rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
match /{document=**} {
allow read, write: if request.auth != null;
}
}
}
I would be happy if somebody could tell me where I am going wrong here.

Answer 1

The first part of the solution was to read the response carefully. It containes the following link https://developers.google.com/identity/sign-in/web/devconsole-project.
Then I had to understand that if you are using the google-identitiy-toolkit you kind of left the firebase-realm and must append the api-key generated in the GC-console (not the firebase-key!) (https://console.cloud.google.com/apis/credentials) to the URL used to fetch the data like this:
GET https://firestore.googleapis.com/v1/projects/<projectId>/databases/(default)/documents/<collection>?key=<google-cloud-api-key>
Accept: application/json
Authorization: Bearer <token from auth response>