Raise ArgumentError when calling change_password! with blank password

[Spone]

Close #329

When calling @user.change_password!("") or @user.change_password!(nil), a ArgumentError exception is now raised, because the password is missing, so it won't be modified.

Please ensure your pull request includes the following:

• Description of changes
• Update to CHANGELOG.md with short description and link to pull request
• Changes have related RSpec tests that ensure functionality does not break

[joshbuker]

Digging through the code, I can't put a finger on where it prevents change_password from accepting a nil/blank password. As far as I can tell, it should pass it to the crypto provider (usually bcrypt), which will accept nil/blank. That said, I tried it locally, and change_password will indeed do nothing if you set the new password as nil/blank.

Not necessarily a blocker on this PR, but I would like to understand better what is going on there.

[Spone]

I only changed the bang version (change_password!). Would it make sense to modify change_password's behavior as well? I'm not sure.

[Spone]

@joshbuker I'm awaiting further instructions here :)

[joshbuker]

At the dentist, I'll take another look and probably merge this in about an hour.

[joshbuker]

Looks good, at some point I should dig more into that code to understand what's going on, and this is a bit of a breaking change API-wise. That said, I suspect it shouldn't be an issue, considering most (all?) applications would raise an error on blank password with the virtual attribute validators anyway.