FIX: update flag reason message with default value (#30026)

Currently only system flags are translated. When we send message to the user that their post was deleted because of custom flag, we should default to custom flag name.

app/models/post.rb

@@ -658,6 +658,7 @@ class Post < ActiveRecord::Base
             "flag_reasons.#{post_action_type_view.types[post_action_type_id]}",
             locale: SiteSetting.default_locale,
             base_path: Discourse.base_path,
+            default: PostActionType.names[post_action_type_id],
           ),
       }
 

lib/post_destroyer.rb

@@ -413,6 +413,7 @@ class PostDestroyer
             "flag_reasons#{".responder" if notify_responders}.#{flag_type}",
             locale: SiteSetting.default_locale,
             base_path: Discourse.base_path,
+            default: PostActionType.flags.find { |flag| flag[:name_key] == flag_type.to_s }[:name],
           ),
       },
     )

spec/lib/post_destroyer_spec.rb

@@ -954,6 +954,29 @@ RSpec.describe PostDestroyer do
       expect(Jobs::SendSystemMessage.jobs.size).to eq(0)
       expect(ReviewableFlaggedPost.pending.count).to eq(0)
     end
+
+    context "when custom flags" do
+      fab!(:custom_flag) { Fabricate(:flag, name: "custom flag", notify_type: true) }
+      let(:third_post) { Fabricate(:post, topic_id: post.topic_id) }
+
+      it "should send message to user with correct translation" do
+        PostActionCreator.new(
+          moderator,
+          third_post,
+          custom_flag.id,
+          is_warning: false,
+          flag_topic: true,
+        ).perform
+        PostDestroyer.new(moderator, third_post, { reviewable: Reviewable.last }).destroy
+        jobs = Jobs::SendSystemMessage.jobs
+        expect(jobs.size).to eq(1)
+
+        Jobs::SendSystemMessage.new.execute(jobs[0]["args"][0].with_indifferent_access)
+
+        expect(Post.last.raw).to match("custom flag")
+        custom_flag.destroy!
+      end
+    end
   end
 
   describe "user actions" do

spec/models/post_spec.rb

@@ -1498,6 +1498,19 @@ RSpec.describe Post do
       ).to(true)
     end
 
+    it "should inform the user when custom flag" do
+      custom_flag = Fabricate(:flag, name: "custom flag")
+      post.hide!(PostActionType.types[:custom_custom_flag])
+
+      jobs = Jobs::SendSystemMessage.jobs
+      expect(jobs.size).to eq(1)
+
+      Jobs::SendSystemMessage.new.execute(jobs[0]["args"][0].with_indifferent_access)
+      expect(Post.last.raw).to match("custom flag")
+
+      custom_flag.destroy!
+    end
+
     it "should decrease user_stat topic_count for first post" do
       expect do post.hide!(PostActionType.types[:off_topic]) end.to change {
         post.user.user_stat.reload.topic_count