The original idea for having different SEPTransactionClientBehaviors (i.e. ClusterSEPTransactionClientBehaviors and DefaultSEPTransactionClientBehaviors) was to force running commands through the mongos service entry point and transforming those to its cluster variant name (“clusterXYZ”).

Now, with SERVER-84183, SEPTransactionClientBehaviors depends on a Service to choose which service entry point (mongos or mongod) operate. Because the RouterService is always present by default on all MongoD (SERVER-85770), this part of the code can be simplified, as there is no real need to have different implementations of SEPTransactionClientBehaviors, thanks to the Service parameter.

The goal of this ticket is to evaluate how the code can be simplified now that the RouterService is always present and the given opCtx returns the service entry point needed for each moment.