Remove legacy case study code [WHIT-3250]

app/components/admin/edition_images/image_component.html.erb

@@ -34,16 +34,6 @@
     <div class="app-view-edition-resource__actions govuk-grid-column-full govuk-button-group govuk-!-margin-top-4">
       <%= link_to("Edit details", edit_admin_edition_image_path(edition, image), class: "govuk-link govuk-!-margin-top-2 app-view-edition-resource__actions__link") %>
       <%= link_to("Delete image", confirm_destroy_admin_edition_image_path(edition, image), class: "govuk-link gem-link--destructive govuk-!-margin-top-2 app-view-edition-resource__actions__link") %>
-
-      <% if can_be_used_as_case_study_lead_image? %>
-        <%= form_with url: admin_edition_lead_image_path(edition, image), method: :patch do |form| %>
-          <%= render "govuk_publishing_components/components/button", {
-            text: "Select as lead image",
-            secondary_solid: true,
-            margin_bottom: 4,
-          } %>
-        <% end %>
-      <% end %>
     </div>
   <% end %>
 </li>

app/components/admin/edition_images/image_component.rb

@@ -22,8 +22,4 @@ def image_markdown
   def find_image_index
     edition.images.find_index(image)
   end
-
-  def can_be_used_as_case_study_lead_image?
-    edition.is_a?(CaseStudy) && image_usage.embeddable? && !image.svg? && !image.image_data.requires_crop?
-  end
 end

app/controllers/admin/edition_images_controller.rb

@@ -33,7 +33,6 @@ def toggle_default_lead_image_behaviour
   def destroy
     filename = image.image_data.carrierwave_image
     image.destroy!
-    @edition.update_lead_image if @edition.is_a?(CaseStudy) # Legacy: remove when CaseStudy migrated to StandardEdition
     PublishingApiDocumentRepublishingJob.perform_async(@edition.document_id, false)
 
     redirect_to admin_edition_images_path(@edition), notice: "#{filename} has been deleted"
@@ -98,7 +97,6 @@ def create
 
     if @images.any? && @images.map(&:valid?).all?
       @images.each(&:save)
-      @edition.update_lead_image if @edition.is_a?(CaseStudy) # Legacy: remove when CaseStudy migrated to StandardEdition
       @edition.update!(image_display_option: nil) if @image_usage.key == "lead"
       PublishingApiDocumentRepublishingJob.perform_async(@edition.document_id, false)
       flash.notice = "Images successfully uploaded"

app/controllers/admin/editions_controller.rb

@@ -6,7 +6,7 @@ class Admin::EditionsController < Admin::BaseController
   before_action :clean_edition_parameters, only: %i[create update]
   before_action :clear_scheduled_publication_if_not_activated, only: %i[create update]
   before_action :clear_response_form_file_cache, only: %i[create update]
-  before_action :find_edition, only: %i[show edit update revise diff confirm_destroy destroy update_bypass_id update_image_display_option features]
+  before_action :find_edition, only: %i[show edit update revise diff confirm_destroy destroy update_bypass_id features]
   before_action :prevent_modification_of_unmodifiable_edition, only: %i[update]
   before_action :delete_absent_edition_organisations, only: %i[create update]
   before_action :build_national_exclusion_params, only: %i[create update]
@@ -33,7 +33,7 @@ def enforce_permissions!
       enforce_permission!(:create, edition_class || Edition)
     when "create"
       enforce_permission!(:create, @edition)
-    when "edit", "update", "revise", "diff", "update_bypass_id", "update_image_display_option", "features"
+    when "edit", "update", "revise", "diff", "update_bypass_id", "features"
       enforce_permission!(:update, @edition)
     when "destroy", "confirm_destroy"
       enforce_permission!(:delete, @edition)

app/helpers/admin/base_path_helper.rb

@@ -3,7 +3,7 @@
 module Admin::BasePathHelper
   MAPPINGS = [
     { "CallForEvidence" => "/government/calls-for-evidence" },
-    { "CaseStudy" => "/government/case-studies" },
+    { "StandardEdition" => "/government/case-studies" },
     { "Consultation" => "/government/consultations" },
     { "DetailedGuide" => "/guidance" },
     { "DocumentCollection" => "/government/collections" },
@@ -20,7 +20,7 @@ module Admin::BasePathHelper
   HTML_ATTACHMENT_PATH_REGEX = %r{
     \A/government/
     (?!statistics/announcements/)  # exclude /government/statistics/announcements/...
-    [^/]+                          # section (e.g. calls-for-evidence, publications, case-studies, etc.)
+    [^/]+                          # section (e.g. calls-for-evidence, publications etc.)
     /[^/]+                         # document slug
     /[^/]+                         # attachment slug
     \z

app/helpers/admin/edition_actions_helper.rb

@@ -61,7 +61,6 @@ def legacy_types_options(user)
     legacy_classes.map { |edition_type|
       next if edition_type == FatalityNotice && !user.can_handle_fatalities?
       next if edition_type == PlanForChangeLandingPage && !user.gds_admin?
-      next if edition_type == CaseStudy
 
       [edition_type.format_name.humanize.pluralize, edition_type.model_name.singular]
     }.compact

app/helpers/admin/republishing_helper.rb

@@ -84,7 +84,6 @@ def bulk_content_type_metadata
   def republishable_content_types
     legacy_editionable_content_types = %w[
       CallForEvidence
-      CaseStudy
       Consultation
       CorporateInformationPage
       DetailedGuide