chore: Add validation to prevent message flooding (#9254)

- Add a validation to limit messages created per minute to avoid message flooding cases.

spec/models/message_spec.rb

@@ -11,7 +11,7 @@ RSpec.describe Message do
   end
 
   describe 'length validations' do
-    let(:message) { create(:message) }
+    let!(:message) { create(:message) }
 
     context 'when it validates name length' do
       it 'valid when within limit' do
@@ -27,6 +27,17 @@ RSpec.describe Message do
         expect(message.errors[:processed_message_content]).to include('is too long (maximum is 150000 characters)')
         expect(message.errors[:content]).to include('is too long (maximum is 150000 characters)')
       end
+
+      it 'adds error in case of message flooding' do
+        with_modified_env 'CONVERSATION_MESSAGE_PER_MINUTE_LIMIT': '2' do
+          conversation = message.conversation
+          create(:message, conversation: conversation)
+          conv_new_message = build(:message, conversation: message.conversation)
+
+          expect(conv_new_message.valid?).to be false
+          expect(conv_new_message.errors[:base]).to eq(['Too many messages'])
+        end
+      end
     end
   end