Require display names to have a minimum unicode width of 3 columns

Fixes #4538

app/validators/width_validator.rb

@@ -0,0 +1,11 @@
+class WidthValidator < ActiveModel::Validations::LengthValidator
+  module WidthAsLength
+    def length
+      Unicode::DisplayWidth.of(to_s)
+    end
+  end
+
+  def validate_each(record, attribute, value)
+    super(record, attribute, value.extend(WidthAsLength))
+  end
+end