validates_uniqueness_of for a String field has case_insensitive option.

By analogy, validates_uniqueness_of for an Array field should have order_insensitive option.

This can be done using this:

validate_uniqueness_of :my_array_field

#=>
# values = my_array_field.uniq
# Klass.where(my_array_field: { "$size" => values.size, "$all" => values }).ne(_id: self._id).exists?

This is not a critical issue but I came across this while coding and thought it would make sense to add.