Add more robust validation to the deploy URL user input on config step

[ymekuria]

Currently the only validation is if the URL is not an empty string. The scope and types of validation are up for discussion. Validation ideas:

-URL validation -minimum length validation -http validation?(maybe some people won't want this)

[bkase]

TODO: Needs a spec before community task

[jasongitmail]

Reviewing with Yoni. We're aligned to close this because doesn't seem necessary