Starting in version 8.0, internal routing capabilities are available by default and no longer depend on the ClusterRole::RouterServer condition.

This implies that ClusterRole::RouterServer can be removed as implicitly set on each MongoD node, but at the same time we need a way to gate routing code. One possible solution is to use the feature flag that currently allow to set the ClusterRole::RouterServer (in other words, the router role is set when the feature flag is enabled).

This implies that ClusterRole::RouterServer can be removed since it is implicitly set on each MongoD node, but at the same time, we need a way to control the routing code. A possible solution would be to reuse thefeatureFlagEmbeddedRouter feature flag that currently allows to set ClusterRole::RouterServer (in other words, the router role is set when the capability flag is enabled).

The goal of this ticket is to evaluate possible alternatives and implement the most reasonable one.

Note: As evaluated in SERVER-84127, the internal routing capabilities won't be FCV-gated in version 8.0.