Add best practices for error handling about ios-handbook

[3lvis]

Unless is a developer error (4XX) we should work with the design team in order to provide a non-blocking UI.

USER INPUT VALIDATION ERROR (NOT NETWORKING)

We agree that when possible we'll validate the user's input.

5XX/REACHABILITY (SERVER ERROR)

Recoverable error

We agree that we'll enqueue the operation, and try again later.

User input error

We let the user know to change their input and try again.

4XX (DEVELOPER ERROR)

We'll show pop up saying we screwed up.

401 AUTHENTICATION ERROR

Have a delegate that lets the user renew a token if needed, this delegate method will return true if the request should be retried, otherwise return false if it should return the error.

[3lvis]

Added one more case based on the scenarios to my current app 401.

[3lvis]

https://uxplanet.org/optimistic-1000-34d9eefe4c05#.ynydub6q8

[3lvis]

That blog post shows some of the concepts I mentioned when we discussed this topic.

[3lvis]

Doing some spring cleaning, please open a new issue if you still want to do this.