[Recipe] Command enrichment

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How to enrich commands before or during dispatch with external data. This data may be looked up from a read model, another service, or an external third party API.

A router middleware defining an enrichment protocol is one possible solution. Here's an example gist with middleware for command enrichment.

Note processing by an aggregate instance during comand execution blocks it from handling any other commands. Whereas router middleware is executed by the dispatching process, before the aggregate instance is called (and is non-blocking to other processes).