Add UrlAttribute concern

[jkostolansky]

This PR introduces UrlAttribute concern to remove http(s)://protocol and custom prefix from URL attributes. It also refactors the existing logic for social profile links (github, ...).

It doesn't add any URL validation because I think it's not necessary at this point. The http(s):// protocol is not required in the submitted data, so even asdf should be valid, because https://asdf is a valid URL.

Resolves #842

[joemasilotti]

This looks great and works exactly how I'd expect it to!

But I think we need a data migration/backfill to update all the existing records. I think this can be accomplished by saving every developer record. But we also need to make sure not to update updated_at because that is used for the "Recently active" badge.

[jkostolansky]

I've added a migration, what do you think? The URL logic is duplicated in the migration, because migrations shouldn't depend on the current application code (that will change in the future).

[joemasilotti]

Sorry, I didn't mean we needed an actual Rails migration. You can throw a couple lines of a script in lib/tasks/backfills.rake that I can run as a one-off on Heroku.

Does that make sense?

[jkostolansky]

🤦‍♂️ Need to think before typing. Sure, makes sense. Changed.

[joemasilotti]

Excellent - thank you!