feat: Child stream that runs after all records synced by parent stream

[ReubenFrankel]

Feature scope

Taps (catalog, state, tests, etc.)

Description

I'm imagining something like

class ParentStream(Stream):

    def get_deferred_child_context(self, records, context)
        return {"record_ids": [record["id"] for record in records]}


class DeferredChildStream(Stream):

    parent_stream_type = ParentStream

    def get_records(self, context):
        for record_id in context["record_ids"]:
            ...

This would useful to support APIs that offer supplemental "detail" endpoints (e,g, GET /resource/details) that accept one or more resource identifiers in bulk (request body data), rather than one at a time (e.g. GET /resources/{id}/details) as is the case in a traditional parent-child stream relationship. I don't really know enough about context or state here to fully understand the implications of something like this, but it feels possible.