Access token lost in transit, when using UserCredentials ToBuilder()

[qcastel]

Environment details

When using the library, I found a bug in the UserCredentials#ToBuilder()
It's not calling super and therefore we lost the access token

Steps to reproduce

UserCredentialsTest.java

  @Test
  public void toBuilder() throws IOException {
    final URI tokenServer1 = URI.create("https://foo1.com/bar");
    AccessToken accessToken = new AccessToken(ACCESS_TOKEN, null);
    MockHttpTransportFactory httpTransportFactory = new MockHttpTransportFactory();
    UserCredentials credentials =
            UserCredentials.newBuilder()
                    .setClientId(CLIENT_ID)
                    .setClientSecret(CLIENT_SECRET)
                    .setRefreshToken(REFRESH_TOKEN)
                    .setAccessToken(accessToken)
                    .setHttpTransportFactory(httpTransportFactory)
                    .setTokenServerUri(tokenServer1)
                    .build();

    credentials.toBuilder().build();
    UserCredentials otherCredentials = credentials.toBuilder().build();
    assertEquals(credentials, otherCredentials);
  }

Will shortly provide a PR for this