Show login failure error and message

[shana]

We need more detailed login failure messages, users can't tell what's wrong based on what we display right now.

[grokys]

It would be good to collect some examples of what we're currently showing and what we should be showing here.

[meaghanlewis]

Agreed. I can do that and update this issue @grokys

[meaghanlewis]

Here are a few examples of login failure messages could be more detailed. There are likely more scenarios I'm missing.

Examples 1-3: Error icon shown when there is a problem

Error icon (❗️) only, no text explaining "no username/email" or "invalid username/email"

Error icon and bad credentials displayed. Which is better than showing nothing like in the example above.

Error icon displayed when server address incorrect. Something like "incorrect server address entered" could be more helpful.

Example 4: No internet connection

This error occurred when I didn't have internet connection. It would be nice to show the specific problem rather than a vague "an error occur while sending the request."

[meaghanlewis]

From: #993 (comment)

However, we can still do better with the error message we display. Currently we only display the "Validation Failed" part of the exception. We should also display the messages in errors:

{
"message":"Validation Failed",
"errors": [ {"resource":"OauthAccess","code":"custom","field":"user","message":"user must have a verified email address in order to authenticate via OAuth"}],
"documentation_url":"https://developer.github.com/v3/oauth_authorizations/#get-or-create-an-authorization-for-a-specific-app"
}

[meaghanlewis]

Renamed this to show the message (ex: "Validation Failed") as well as the error message( ex. "user must have a verified email address in order to authenticate via OAuth"