I'm using 'firebase-admin' for node to create custom tokens based on users created using admin.auth().createUser(params) and updated via admin.auth().updateUser(userId, updateParams)
However, when a custom user is created, such user's "signed in" field is "null" in the Firebase Authentication Dashboard as well as when I fetch user record using admin.auth().getUser('custom:uid').then((userRecord) => { console.log(userRecord.toJSON()); })
Below is the result from fetching user record (I have masked credentials):
{ uid: 'custom:uid', email: '[email protected]', emailVerified: false, displayName: 'testuser', photoURL: 'https://xxxx.jpg', phoneNumber: undefined, disabled: false, metadata: { lastSignInTime: null, creationTime: 'Mon, 29 Mar 2021 08:11:56 GMT' }, passwordHash: undefined, passwordSalt: undefined, customClaims: undefined, tokensValidAfterTime: 'Mon, 29 Mar 2021 08:11:56 GMT', tenantId: undefined, providerData: [] }
and below is my dashboard screenshot:

My question is what should I do to update 'lastSignInTime', so that it correctly updates upon a user sign in? I assumed that either when I createUser() or updateUser(), Firebase shall automatically record the "Signed In" field (as it did for "Created"), which it did not do.