Anything else a resource needs.
OptionaleventThe event being answered, for a resource that needs more than the parameters above.
Typed by the resource for the same reason, and unknown by default because the module is
agnostic of the platform the event came from.
OptionalfieldsRequested sparse fieldset: narrows the output to these top-level keys.
OptionalfragmentThe requested fragment, when the caller asked for one by name.
OptionalincludeRequested relations to embed.
OptionalprincipalThe authenticated principal, when the application has one.
Typed by the resource, because deciding what a caller may see is the most common reason two
callers get different shapes, and unknown makes every such decision a cast. The default stays
unknown: this module never assumes an application has users, let alone what a user is.
The context a projection is given.
Open on purpose: a resource reads whatever it needs, and the middleware fills in what the request carried. The authenticated principal is part of it, because deciding what a caller may see is the most common reason a projection differs between two callers.