Fix Set key type for isBatchKeyASet + ts-reset

[jack-guy]

Following the release of TypeScript types in #355 there is one single error remaining in our internal service. It looks like TypeScript + ts-reset does not infer a string union type when using the getNewKeyTypeFromBatchKeySetType helper, according to this rule:

Make Set.has() less strict

src/graphql/dataloaders/__codegen__/foo_loaders.ts:x:y - error TS2345: Argument of type '{ foo: Set<string>; }' is not assignable to parameter of type 'Readonly<{ foo: Set<"BAR" | "BAZ">; }>'.
  Types of property 'foo' are incompatible.
    Type 'Set<string>' is not assignable to type 'Set<"BAR" | "BAZ">'.
      Type 'string' is not assignable to type '"BAR" | "BAZ"'.

1050                       ...__resourceArgs,
                           ~~~~~~~~~~~~~~~~~

Because of the reset override, TypeScript infers the parameter type of Set.prototype.has to be a string, rather than the generic type of the Set.

We can fix this by using a type inference instead, T extends Set<infer U> ? U : never;. This is arguably the more "correct" way to do it anyway.

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After linking in the patched dataloader-codegen we no longer have any type errors in our dataloaders. I did not add a regression test as this is specific to users of ts-reset and the existing coverage from testExampleTypes/swapi.ts should cover the happy path.

[magicmark]

makes sense to me, nice fix!

[jack-guy]

This should have been released in 1.0.2 but I forgot to hit the merge button again 🙃

this will be 1.0.3 now. Sorry about that!