Description

From the documentation "Sharded Cluster Components" up to version 3.2, we have mentioned that client affinity is required if load balancer is running between the application and the mongos:

> You may also deploy a group of mongos instances and use a proxy/load balancer between the application and the mongos. In these deployments, you must configure the load balancer for client affinity so that every connection from a single client reaches the same mongos.

However, this was no longer mentioned since the [v3.4 documentation](https://docs.mongodb.com/v3.4/core/sharded-cluster-components/#production-configuration). Since this is still a requirement, please add this to the documentation.

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