Improve UX of auth routes on connection failure

[wbazant]

Follow-up to #562 about auth routes. Currently, if the request to log in fails due to bad connection (or something unforeseen), we don't handle it well. Instead, we want to show error messages:

• Sign up failed: {error.message}
• Confirm account failed: {error.message}
• Sign in failed: {error.message}
• Resetting password failed: {error.message}
• Setting new password failed: {error.message} etc.

We will localize these messages later.

If someone wants to work on this as a first issue - you can just do one form first, maybe start from the most important one or the one that seems easiest.

To test: open the form, and turn off the network in the browser tab or cut off internet access to your computer. Then submit each form, and make sure the error is understandable.

Also, try to use the form afterwards - log in correctly, log in with wrong password, etc. when the network is on. , and make sure it still works.

[ahmedhalac]

Hi @wbazant. Can you assign me on this?

[wbazant]

Assigned you the issue, thanks for taking it on! If you want it reviewed bit by bit - maybe one route first - feel free to create child issues, or you can take them on all at once.