Replace attribute_changed? in before callbacks

This method is deprecated in Rails 5.1 because its behavior will be
different in `before` and `after` callbacks.

Here we're replacing the deprecated `attribute_changed?` and
`attribute_was` with `will_save_change_to_attribute?` and
`attribute_in_database` during `before_save` callbacks.

https://github.com/rails/rails/pull/32835/

app/models/budget/investment.rb

@@ -396,7 +396,7 @@ class Budget
     private
 
       def set_denormalized_ids
-        self.group_id = heading&.group_id if heading_id_changed?
+        self.group_id = heading&.group_id if will_save_change_to_heading_id?
         self.budget_id ||= heading&.group&.budget_id
       end
 

app/models/poll/partial_result.rb

@@ -19,10 +19,10 @@ class Poll::PartialResult < ApplicationRecord
   before_save :update_logs
 
   def update_logs
-    if amount_changed? && amount_was.present?
-      self.amount_log += ":#{amount_was}"
-      self.officer_assignment_id_log += ":#{officer_assignment_id_was}"
-      self.author_id_log += ":#{author_id_was}"
+    if will_save_change_to_amount? && amount_in_database.present?
+      self.amount_log += ":#{amount_in_database}"
+      self.officer_assignment_id_log += ":#{officer_assignment_id_in_database}"
+      self.author_id_log += ":#{author_id_in_database}"
     end
   end
 end

app/models/poll/recount.rb

@@ -20,9 +20,9 @@ class Poll::Recount < ApplicationRecord
     amounts_changed = false
 
     [:white, :null, :total].each do |amount|
-      next unless send("#{amount}_amount_changed?") && send("#{amount}_amount_was").present?
+      next unless send("will_save_change_to_#{amount}_amount?") && send("#{amount}_amount_in_database").present?
 
-      self["#{amount}_amount_log"] += ":#{send("#{amount}_amount_was")}"
+      self["#{amount}_amount_log"] += ":#{send("#{amount}_amount_in_database")}"
       amounts_changed = true
     end
 
@@ -30,7 +30,7 @@ class Poll::Recount < ApplicationRecord
   end
 
   def update_officer_author
-    self.officer_assignment_id_log += ":#{officer_assignment_id_was}"
-    self.author_id_log += ":#{author_id_was}"
+    self.officer_assignment_id_log += ":#{officer_assignment_id_in_database}"
+    self.author_id_log += ":#{author_id_in_database}"
   end
 end