Ignore error if mentioned account was not processable (#29215)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

spec/workers/mention_resolve_worker_spec.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe MentionResolveWorker do
+  let(:status_id) { -42 }
+  let(:uri) { 'https://example.com/users/unknown' }
+
+  describe '#perform' do
+    subject { described_class.new.perform(status_id, uri, {}) }
+
+    context 'with a non-existent status' do
+      it 'returns nil' do
+        expect(subject).to be_nil
+      end
+    end
+
+    context 'with a valid user' do
+      let(:status) { Fabricate(:status) }
+      let(:status_id) { status.id }
+
+      let(:service_double) { instance_double(ActivityPub::FetchRemoteAccountService) }
+
+      before do
+        allow(ActivityPub::FetchRemoteAccountService).to receive(:new).and_return(service_double)
+
+        allow(service_double).to receive(:call).with(uri, anything) { Fabricate(:account, domain: 'example.com', uri: uri) }
+      end
+
+      it 'resolves the account and adds a new mention', :aggregate_failures do
+        expect { subject }
+          .to change { status.reload.mentions }.from([]).to(a_collection_including(having_attributes(account: having_attributes(uri: uri), silent: false)))
+
+        expect(service_double).to have_received(:call).once
+      end
+    end
+  end
+end