API JSON: a flow's payload and a dependency's prefix metadata differ from the metamodel

[someshSandbox]

Both are documented choices in rdf-mapping.md, so this is a request, not a bug report. For the API's JSON form, could they follow the metamodel?

Source	Exported (documented at)	Grammar (SysML-textual-bnf)
flow of Fuel from a.p.fuel to b.p.fuel; (the flow example in #651)	sysx:payload → a FeatureReferenceExpression under an OwningMembership (rdf-mapping.md:532)	FeatureMembership owning a PayloadFeature (:845-852)
#Tag dependency x to y;	MetadataUsage under an OwningMembership of the dependency (rdf-mapping.md:458-466)	an Annotation whose annotatingElement is the MetadataUsage (:51-53, :1660-1662)

package A {
    metadata def Tag;
    part x;
    part y;
    #Tag dependency x to y;
}

A reader of standard API JSON finds no payload feature on the flow, and no annotation on the dependency.

:532 gives the reason for the payload: the 202407 ontology table has no payloadFeature property. The API form reads metaclasses rather than that table, so it could carry the PayloadFeature even if Turtle keeps the expression.

[devin-ai-integration]

Both halves are fixed on develop and shipped in v0.9.1:

• fix(export): a dependency's prefix metadata is an owned Annotation (#652) #707 — a dependency's #Tag prefix is written as an Annotation the dependency owns (annotatedElement the dependency, annotatingElement the MetadataUsage), in Turtle and in API JSON.
• fix(export): a flow's payload is a PayloadFeature (#652) #708 — a flow's payload is a PayloadFeature under a FeatureMembership, with its typing, multiplicity and value; sysx:payload is no longer written for a flow.

Verified on current develop with the model in this issue: sysml -convert api-json emits the PayloadFeature on the flow and the Annotation on the dependency, and no sysx:payload.