Rate-limit new conversations

The creation of new conversations from the client SDK should be rate-limited to prevent abuse. Furthermore, the amount of concurrent conversations a customer is able to have opened at any given time should be limited.

This two basic controls should prevent abuse of the platform and the cost incurred by enterprise from handling and mitigation when it occurs.

This is specially impactful on clients with ticketing automation in place (such as Zendesk AI) as the cost incurred is automatic and proportional to the size of the attack.