Add and apply rubocop rules for empty lines

We were very inconsistent regarding these rules.

Personally I prefer no empty lines around blocks, clases, etc... as
recommended by the Ruby style guide [1], and they're the default values
in rubocop, so those are the settings I'm applying.

The exception is the `private` access modifier, since we were leaving
empty lines around it most of the time. That's the default rubocop rule
as well. Personally I don't have a strong preference about this one.


[1] https://rubystyle.guide/#empty-lines-around-bodies

app/controllers/management/document_verifications_controller.rb

@@ -1,5 +1,4 @@
 class Management::DocumentVerificationsController < Management::BaseController
-
   before_action :clean_document_number, only: :check
   before_action :set_document, only: :check
 
@@ -48,5 +47,4 @@ class Management::DocumentVerificationsController < Management::BaseController
       return if params[:document_verification][:document_number].blank?
       params[:document_verification][:document_number] = params[:document_verification][:document_number].gsub(/[^a-z0-9]+/i, "").upcase
     end
-
 end