improve validation of origin params to API calls

[lloyd]

as @fmarier pointed out in issue #1979, we can do much better with our regex in validate.js - more tightly validating incoming origins.

Not extremely high priority, but why not?

for reference, http://blog.gnukai.com/2010/06/fqdn-regular-expression/

[lloyd]

@zaach - you want?

[zaach]

That's a wicked regex. I'm on it.

[fmarier]

One thing that I'll be doing soon is refactoring the code that extract the domain from an email address (GH-1994). Once I do that, I'll validate the extracted domain, just in case.

So I would suggest that we create a domain/hostname validation function that the origin type checking code could use to check the hostname part of the origin. Or perhaps we should create a new 'hostname' type instead?