Enhancement

Label names in chatwoot only support alphabets, numbers, hyphen and underscore.
At the moment the available validation doesn't show the user any errors, which would leave the user confused.

So let's add a validation error describing this behaviour

Current behaviour

<img width="1273" alt="Screenshot 2020-10-02 at 4 29 03 PM" src="https://user-images.githubuserconten

Problem
This query could be made more efficient. We currently fetch all conversations ordered by :inserted_at, while in the UI we display them based on how recently a message was sent within it (i.e. message.sent_at).

Solution
Optimize this query to order the results by the most recently sent message associated with the conversation.

It might also be helpful to write a query to