Support Validating Multiple Emails in a Single String

[sshaw]

Often times one allows a user to enter multiple emails separated by a comma or newline. It would be nice if this library supported validating these. Currently doing this by hand with ValidatesEmailFormatOf.validate_email_format.

[alexdunae]

Interesting... I just closed a PR that was proposing this since I thought it was a pretty niche requirement.

My instinct would be to create a manual validation instead, letting you split on whatever characters your application needs and handling duplication etc... Even more so considering the application will need to split and iterate on the emails anyways.