Add attribute validation for models

[jstoone]

What needs to be done

• Allow models to define Laravel validation rules to attributes
• Validation should happen before the future is created
• And return validation error messages upon failing
• And return true upon a passing validation

Why is this appropriate

Currently invalid data could be scheduled for change, which could lead to uncaught bugs in the future. So this allows the user to preemptively guard for e.g a string being passed to a boolean/tinyint field.