MissingPresenceValidation should ignore enum's with default values

[fidalgo]

If you have a model, where an enum is defined with a default (or _default_ keyword) like this:

class Profile < ApplicationRecord
    enum kind: {general: 0, admin: 1}, _default: :general
end

The report should not include a missing presence validator for the field.

[gregnavis]

This doesn't sound like a bug as a default value doesn't prevent the color from creating a model with an explicit nil value. For example:

Profile.create!(kind: nil)

I think in this case active_record_doctor discovered an actual bug or edge case in your code. I recommend that you ignore that warning via configuration or add a strict validator.