[SDK-2588] Avoid multiple simultaneous HTTP calls

[frederikprijck]

There appears to be a bug in lock that can result in multiple, simultaneuour, HTTP calls to the /login endpoint(s).

To reproduce:
In lock, try the following In Chrome:
• Ensure username/email and password are filled in
• Focus the username/email field
• hit enter twice fast

Network tab should show multiple calls to login.

In safari, this issue exists on both fields, not only username/email.

The reason the behavior is different in Chrome and Safari seems to be because Chrome avoids submitting the form when pressing enter in a disabled input. Password is the only field that is getting disabled when the form is being submitted.

The fix here is to ensure both username and email fields are also disabled while the form is being submitted.

On safari however, it appears that safari does not respect the disabled value and still submits the form. Therefor I changed the fix that was done in #1968, by using the isSubmitting value instead of the disableSubmitButton

[frederikprijck]

Marked as draft as I believe it can benefit from a test or two.

[stevehobbsdev]

I'm having trouble adding an acceptance test that will automatically test this scenario; trying to add something that will fire a key event for the "enter" key that submits a form appears to be impossible, as the browser just ignores it.

This issue on SO is a little old but demonstrates the same problem.

Happy to proceed with the fix given that manual testing can show that the bug has been mitigated.

[frederikprijck]

Sure, let's proceed!

[stevehobbsdev]

LGTM