The client_id to be sent to the authentication server (see https://tools.ietf.org/html/rfc6749#appendix-A.1).

This should only be
used for statistics or logging etc. as it cannot actually be trusted since
it could have been manipulated on the client!

Sets whether the authenticator automatically refreshes access tokens if the server supports it.

Sets whether the authenticator use the scope when refreshing access tokens if the server supports it.

The endpoint on the server that authentication and token refresh requests are sent to.

The endpoint on the server that token revocation requests are sent to. Only set this if the server actually supports token revocation. If this is null, the authenticator will not revoke tokens on session invalidation.

If token revocation is enabled but fails, session invalidation will be
intercepted and the session will remain authenticated (see
OAuth2PasswordGrantAuthenticator.invalidate.

The offset time in milliseconds to refresh the access token. This must return a random number. This randomization is needed because in case of multiple tabs, we need to prevent the tabs from sending refresh token request at the same exact moment.

When overriding this property, make sure to mark the overridden property
as volatile so it will actually have a different value each time it is
accessed.

Authenticates the session with the specified identification, password and optional scope; issues a POST request to the OAuth2PasswordGrantAuthenticator.serverTokenEndpoint and receives the access token in response (see https://tools.ietf.org/html/rfc6749#section-4.3).

If the credentials are valid (and the optionally requested scope is
granted) and thus authentication succeeds, a promise that resolves with the
server's response is returned, otherwise a promise that rejects with the
error as returned by the server is returned.

If the
server supports it, this
method also schedules refresh requests for the access token before it
expires.

The server responses are expected to look as defined in the spec (see
http://tools.ietf.org/html/rfc6749#section-5). The response to a successful
authentication request should be:

```json
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8

{
  "access_token":"2YotnFZFEjr1zCsicMWpAA",
  "token_type":"bearer",
  "expires_in":3600, // optional
  "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA" // optional
}
```

The response for a failing authentication request should be:

```json
HTTP/1.1 400 Bad Request
Content-Type: application/json;charset=UTF-8

{
  "error":"invalid_grant"
}
```

A full list of error codes can be found
[here](https://tools.ietf.org/html/rfc6749#section-5.2).

If token revocation is enabled, this will revoke the access token (and the refresh token if present). If token revocation succeeds, this method returns a resolving promise, otherwise it will return a rejecting promise, thus intercepting session invalidation.

If token revocation is not enabled this method simply returns a resolving
promise.

Makes a request to the OAuth 2.0 server.

Restores the session from a session data object; will return a resolving promise when there is a non-empty access_token in the session data and a rejecting promise otherwise. If the server issues expiring access tokens and there is an expired access token in the session data along with a refresh token, the authenticator will try to refresh the access token and return a promise that resolves with the new access token if the refresh was successful. If there is no refresh token or the token refresh is not successful, a rejecting promise will be returned.

Triggered when the authenticator refreshed the access token (see RFC 6749, section 6).