[EVE-39] Expose endpoint configuration for command mapping

[alexeyzimarev]

It's now possible to add things like authorisation policies using the same way as one would do it with minimal API, when using MapCommand<T1, T2, TAggtegate> or MapCommand<T, TAggregate>. But when one uses MapAggregateCommands<TAggtegate> and chains MapCommand, the function returns the command route builder, so the endpoint cannot be configured additionally.

It can be solved by adding a configuration function (optional) to add the necessary additions to a given mapped endpoint.

_{From SyncLinear.com | EVE-39}