Allow reports with long comments from remote instances, but truncate (#25028)

spec/lib/activitypub/activity/flag_spec.rb

@@ -39,6 +39,37 @@ RSpec.describe ActivityPub::Activity::Flag do
       end
     end
 
+    context 'when the report comment is excessively long' do
+      subject do
+        described_class.new({
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          id: flag_id,
+          type: 'Flag',
+          content: long_comment,
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: [
+            ActivityPub::TagManager.instance.uri_for(flagged),
+            ActivityPub::TagManager.instance.uri_for(status),
+          ],
+        }.with_indifferent_access, sender)
+      end
+
+      let(:long_comment) { Faker::Lorem.characters(number: 6000) }
+
+      before do
+        subject.perform
+      end
+
+      it 'creates a report but with a truncated comment' do
+        report = Report.find_by(account: sender, target_account: flagged)
+
+        expect(report).to_not be_nil
+        expect(report.comment.length).to eq 5000
+        expect(report.comment).to eq long_comment[0...5000]
+        expect(report.status_ids).to eq [status.id]
+      end
+    end
+
     context 'when the reported status is private and should not be visible to the remote server' do
       let(:status) { Fabricate(:status, account: flagged, uri: 'foobar', visibility: :private) }