Turning GQLExtend to extend type keywords instead of extends directive

[coderfromhere]

Hi!

I wonder if there's a way to instruct schema renderer responsible for api.render attribute to use extend keywords on defined types instead of the @extends directive in the resulting SDL? Apollo docs seem to discourage use of the directive in favour of the keyword.

I.e. turning this:

type Query @extends { ... }

into this

extend type Query { ... }

[dariuszkuc]

FYI @extends directive/extend type syntax is no longer needed for Federation v2 and should generally be omitted from the schema. Extending types is still a useful functionality and there are valid use cases for it (but federation v2 does not require it all).

[paulpdaniels]

I Think we could handle this by moving GQLExtend into core and detecting it the way we do GQLDeprecated during derivation. Then we can just deprecate the one in the federation package.