Apollo Federation & Gateway, type extension support

[michaeldgraham]

This PR includes initial support for Apollo Federation & Gateway and every kind of type extension.

Support is also added for using a gql string literal tag on the typeDefs SDL string provided to makeAugmentedSchema and for a new cypher tag used when writing the statement argument of a @cypher directive, resulting in embedded Cypher syntax highlighting in supporting editors.

The type extension support should resolve the following issues:

• @cypher doesn't work in extend type Query #395 - @cypher doesn't work in extend type Query
• Authorization schema directives are ignored on extended types #389 - Authorization schema directives are ignored on extended types
• Type extensions not working #208 - Type extensions not working
• Can't augment schema with filters for extended types. #413 - Can't augment schema with filters for extended types

Feature requests implemented:

• Feature request: makeAugmentedSchema and Apollo's buildFederatedSchema integration support #260 - Feature request: makeAugmentedSchema and Apollo's buildFederatedSchema integration support
• Feature request: Allow augmentation to accept parsed typeDefs from 'gql' tag #422 - Feature request: Allow augmentation to accept parsed typeDefs from 'gql' tag
• Feature request: A 'cypher' template literal tag for @cypher statements #425 - Feature request: A 'cypher' template literal tag for @cypher statements

A guide for using Federation & Gateway has been added to the documentation here. and the documentation for type extensions can be found here, on grandstack.io.

[emregency]

That’s one of the most exciting PRs I have ever seen. 🎉