GraphQL 16 compatibility

[aaronadamsCA]

Make the toolkit compatible with GQL 16.

The only problem I see is this visitor, which is causing TypeError: visitFn.call is not a function:

gatsby-graphql-toolkit/src/compile-node-queries/ast-transformers/remove-unused-fragments.ts

Lines 11 to 42 in b395feb

	return {
	enter: {
	FragmentSpread: node => {
	currentSpreads.push(node.name.value)
	},
	},
	leave: {
	OperationDefinition: node => {
	if (!node.name?.value) {
	throw new Error("Every query must have a name")
	}
	definitionSpreads.set(node.name.value, currentSpreads)
	currentSpreads = []
	},
	FragmentDefinition: node => {
	definitionSpreads.set(node.name.value, currentSpreads)
	currentSpreads = []
	},
	Document: node => {
	const operations = node.definitions.filter(isOperation)
	const operationNames = operations.map(op => op.name?.value)
	const usedSpreads = new Set(
	operationNames.reduce(collectSpreadsRecursively, [])
	)
	const usedFragments = node.definitions.filter(
	node => isFragment(node) && usedSpreads.has(node.name.value)
	)
	return GraphQLAST.document([...operations, ...usedFragments])
	},
	},
	}

Support for enter and leave objects was dropped in GraphQL 16 (graphql/graphql-js#2957), so the visitor would just need to be rewritten in this format:

visit(ast, {
  Kind: {
    enter(node) {
      // enter the "Kind" node
    }
    leave(node) {
      // leave the "Kind" node
    }
  }
})

I've patched this locally, and otherwise everything seems to be working fine.

[AbdallahAbis]

@aaronadamsCA Is there a workaround while waiting for the PR to be merged? I'm trying to use the Toolkit to source from Sanity CMS.

[cameronbraid]

This is also needed for gatsby 5