Refactor dpo_user method and use association to get requestor information

app/models/merge_request.rb

@@ -3,6 +3,7 @@ class MergeRequest < ApplicationRecord
   has_many :merge_request_organisations
   belongs_to :absorbing_organisation, class_name: "Organisation", optional: true
   has_many :merging_organisations, through: :merge_request_organisations, source: :merging_organisation
+  belongs_to :requestor, class_name: "User", foreign_key: "requester_id"
   validate :organisation_name_uniqueness, if: :new_organisation_name
   validates :new_telephone_number, presence: true, if: -> { telephone_number_correct == false }
 
@@ -32,11 +33,7 @@ class MergeRequest < ApplicationRecord
     absorbing_organisation&.name || ""
   end
 
-  def requesting_user
-    User.find(requester_id) if requester_id
-  end
-
   def dpo_user
-    absorbing_organisation.users.filter_by_active.find_by(is_dpo: true) if absorbing_organisation
+    absorbing_organisation.data_protection_officers.filter_by_active.first
   end
 end

app/views/merge_requests/show.html.erb

@@ -37,7 +37,7 @@
 <% end %>
 
 <% request_details = [
-  { label: "Requester", value: display_value_or_placeholder(@merge_request.requesting_user&.name) },
+  { label: "Requester", value: display_value_or_placeholder(@merge_request.requestor&.name) },
   { label: "Helpdesk ticket", value: @merge_request.helpdesk_ticket.present? ? link_to("#{@merge_request.helpdesk_ticket} (opens in a new tab)", "https://dluhcdigital.atlassian.net/browse/#{@merge_request.helpdesk_ticket}", target: "_blank", rel: "noopener noreferrer") : display_value_or_placeholder(nil), action: @merge_request.status == "request_merged" ? nil : { text: "Change", href: "#", visually_hidden_text: "helpdesk ticket" } },
   { label: "Status", value: status_tag(@merge_request.status) },
 ] %>

spec/views/merge_requests/details.html.erb_spec.rb

@@ -24,7 +24,7 @@ RSpec.describe "merge_requests/details.html.erb", type: :view do
 
   it "displays the requester details" do
     expect(rendered).to have_selector("dt", text: "Requester")
-    expect(rendered).to have_selector("dd", text: merge_request.requesting_user&.name || "You didn't answer this question")
+    expect(rendered).to have_selector("dd", text: merge_request.requestor&.name || "You didn't answer this question")
   end
 
   it "displays the helpdesk ticket details" do