Apollo Federation v2.8, v2.9 and v2.10 support

Product

Hot Chocolate

Is your feature request related to a problem?

HotChocolate currently provides support for Apollo Federation up to version 2.7. It would be great the library could be updated with additional support for Federation v2.8 and v2.9.

Changelog

• Federation v2.8 added support for sharing contextual data between different subgraphs (with ancestor <-> descendant) relationship (docs)
• Federation v2.9 added support for demand control based on the IBM Cost spec (docs)
• Federation v2.10 is all about connectors so there is actually nothing to implement here from the subgraph perspective (its just bumping the fed spec version in the @link import)

NOTEs:

• Apollo Federation v2.9 @cost directive definition diverges from the IBM Cost spec as instead of supporting arbitrary cost formula, it requires Int value.

The solution you'd like

Built-in support for latest Apollo Federation versions.

Start with src/HotChocolate/ApolloFederation/src/ApolloFederation/FederationVersion.cs, which currently defines support through Federation 2.7, then read the linked Apollo Federation documentation for the 2.8 and 2.9 directives and the 2.10 version change. Done means built-in support is updated for Federation 2.8, 2.9, and 2.10, including the noted @cost behavior.