feat: support reply to for outgoing message in WhatsApp (#8107)

- This PR enables replies to WhatsApp.

app/services/messages/in_reply_to_message_builder.rb

@@ -0,0 +1,24 @@
+class Messages::InReplyToMessageBuilder
+  pattr_initialize [:message!, :in_reply_to!, :in_reply_to_external_id!]
+
+  delegate :conversation, to: :message
+
+  def perform
+    set_in_reply_to_attribute if @in_reply_to.present? || @in_reply_to_external_id.present?
+  end
+
+  private
+
+  def set_in_reply_to_attribute
+    @message.content_attributes[:in_reply_to_external_id] = in_reply_to_message.try(:source_id)
+    @message.content_attributes[:in_reply_to] = in_reply_to_message.try(:id)
+  end
+
+  def in_reply_to_message
+    return conversation.messages.find_by(id: @in_reply_to) if @in_reply_to.present?
+
+    return conversation.messages.find_by(source_id: @in_reply_to_external_id) if @in_reply_to_external_id
+
+    nil
+  end
+end