Add and apply Layout/DotPosition rule

Since IRB has improved its support for multiline, the main argument
towars using a trailing dot no longer affects most people.

It still affects me, though, since I use Pry :), but I agree
leading dots are more readable, so I'm enabling the rule anyway.

app/models/verification/management/managed_user.rb

@@ -2,8 +2,8 @@ class Verification::Management::ManagedUser
   include ActiveModel::Model
 
   def self.find(document_type, document_number)
-    User.where.not(document_number: nil).
-    find_or_initialize_by(document_type:   document_type,
+    User.where.not(document_number: nil)
+    .find_or_initialize_by(document_type:   document_type,
                           document_number: document_number)
   end
 end