feat: outbound voice call essentials (#12782)

- Enables outbound voice calls in voice channel . We are only caring
about wiring the logic to trigger outgoing calls to the call button
introduced in previous PRs. We will connect it to call component in
subsequent PRs

ref: #11602 

## Screens

<img width="2304" height="1202" alt="image"
src="https://github.com/user-attachments/assets/b91543a8-8d4e-4229-bd80-9727b42c7b0f"
/>

<img width="2304" height="1200" alt="image"
src="https://github.com/user-attachments/assets/1a1dad2a-8cb2-4aa2-9702-c062416556a7"
/>

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Vishnu Narayanan <vishnu@chatwoot.com>

app/builders/messages/message_builder.rb

@@ -138,6 +138,7 @@ class Messages::MessageBuilder
       private: @private,
       sender: sender,
       content_type: @params[:content_type],
+      content_attributes: content_attributes.presence,
       items: @items,
       in_reply_to: @in_reply_to,
       echo_id: @params[:echo_id],
@@ -222,3 +223,5 @@ class Messages::MessageBuilder
                                        })
   end
 end
+
+Messages::MessageBuilder.prepend_mod_with('Messages::MessageBuilder')