Use semantic work package identifier in sharing email links

The shared-work-package email built its "Open work package" link and its
text-part heading from the numeric primary key, so recipients on a
semantic-identifier instance still landed on /work_packages/<numeric-id>
rather than the semantic URL.

Pass the work package itself to the URL helper so to_param yields the
display id, and render the text heading with formatted_id to match the
other work package mailers. Also drops an unused @notification_url that
carried the same numeric-id problem.

STC-747

app/mailers/sharing_mailer.rb

@@ -40,8 +40,7 @@ class SharingMailer < ApplicationMailer
     @work_package = membership.entity
 
     role = membership.roles.first
-    @url = optionally_activated_url(work_package_url(@work_package.id), @invitation_token)
-    @notification_url = optionally_activated_url(details_notifications_url(@work_package.id, tab: :activity), @invitation_token)
+    @url = optionally_activated_url(work_package_url(@work_package), @invitation_token)
 
     set_open_project_headers(@work_package)
     message_id(membership, sharer)

app/views/sharing_mailer/shared_work_package.text.erb

@@ -18,9 +18,9 @@
 %>
 <%= "-" * 100 %>
 
-<%= "=" * (("# " + @work_package.id.to_s + @work_package.subject).length + 4) %>
-= #<%= @work_package.id %> <%= @work_package.subject %> =
-<%= "=" * (("# " + @work_package.id.to_s + @work_package.subject).length + 4) %>
+<%= "=" * ("#{@work_package.formatted_id} #{@work_package.subject}".length + 4) %>
+= <%= @work_package.formatted_id %> <%= @work_package.subject %> =
+<%= "=" * ("#{@work_package.formatted_id} #{@work_package.subject}".length + 4) %>
 
 <%= I18n.t("mail.work_packages.reason.shared") %>:
 <%= t("mail.sharing.work_packages.allowed_actions_html", allowed_actions: @allowed_work_package_actions.to_sentence) %>

spec/mailers/sharing_mailer_spec.rb

@@ -64,6 +64,11 @@ RSpec.describe SharingMailer do
         expect(mail.subject)
           .to eq(I18n.t("mail.sharing.work_packages.subject", id: "##{work_package.id}"))
       end
+
+      it "links to the work package by its numeric id" do
+        expect(mail.html_part.body.encoded).to include("/work_packages/#{work_package.id}")
+        expect(mail.text_part.body.encoded).to include("/work_packages/#{work_package.id}")
+      end
     end
 
     context "with semantic mode",
@@ -81,6 +86,19 @@ RSpec.describe SharingMailer do
         expect(mail.subject)
           .to eq(I18n.t("mail.sharing.work_packages.subject", id: "PROJ-42"))
       end
+
+      it "links to the work package by its semantic identifier, not the numeric id" do
+        expect(mail.html_part.body.encoded).to include("/work_packages/PROJ-42")
+        expect(mail.html_part.body.encoded).not_to include("/work_packages/#{work_package.id}")
+
+        expect(mail.text_part.body.encoded).to include("/work_packages/PROJ-42")
+        expect(mail.text_part.body.encoded).not_to include("/work_packages/#{work_package.id}")
+      end
+
+      it "renders the text-part heading with the semantic identifier, not the numeric id" do
+        expect(mail.text_part.body.encoded).to include("= PROJ-42 #{work_package.subject} =")
+        expect(mail.text_part.body.encoded).not_to include("##{work_package.id}")
+      end
     end
 
     it "has a project header" do