feat: modify "Manage Google Accounts" button to rely on gcloud ADC

[diegomarquezp]

This modifies the behavior of this button in the following way:

• If ADC are not set, it will show a clickable entry explaining the user is not logged in
  
• Clicking this will show more information
  
• If set, it will offer to view the current account.
  
  • Clicking this button will display a singleton list of users (only user associated with ADC)
  • This used to have two buttons to sign in with a different user or log out. It will now show an avatar and email only. No action on click.

NOTE

(fixed - see below) The ADC credentials are cached in google-auth-library-java (see). Running gcloud auth application-default login|revoke will not update this component properly:

1. plugin starts with ADC set
2. run gcloud auth ... revoke
3. menu button will still show as if ADC are set

this is fixed in #3716

[burkedavison]

If a new user see this, it seems reasonable they'd have one of two thoughts:

• I don't know how to do that.
• I should go execute gcloud auth login

But neither of these is the action we're looking to have completed.

Rather than fitting the request in the disabled menu item, do we need to open the dialog and display more information about specifically what we're asking the user to do?

[diegomarquezp]

Makes sense - I will use a separate dialog

[burkedavison]

Since we're using Optional, consider replacing isPresent()+get() with:

account.getName().ifPresent(name::setText);

[burkedavison]

Syntax sugar (meaning: your choice, but consider for readability) -- a private getAccounts() method would prevent needing to have this relatively clunky "declare then initialize then use" order of events.

private List<Account> getAccounts() {
  try {
    return Collections.singletonList(apiFactory.getAccount());
  } catch (IOException ex) {
    ...
    return Collections.emptyList();
  }
}
void createAccountsPane(...) {
  for (Account account : getAccounts()) {
    ...
  }
}

[burkedavison]

Are we certain this is efficient enough to be running every two seconds?

If we were to change some assumptions (like, displaying the login status in the menu) could we turn this from a polling implementation to a on-demand check?

[diegomarquezp]

This polling approach was what I tried when noticing that updating the ADC did not reflect in the oauth library due to caching (fixed in #3716). I will move checkLoggedIn to isEnabled

[diegomarquezp]

Temporary, as better approach is used in #3713

[burkedavison]

If this returns null, then the above account.getName() and account.getEmail() will throw a NullPointerException.