Improve type-safety of admin meta GraphQL API implementation

[emmatown]

No description provided.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 468ed74

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@keystone-next/admin-ui	Major
@keystone-next/keystone	Patch
@keystone-next/example-auth	Patch
@keystone-next/app-basic	Patch
@keystone-next/example-ecommerce	Patch
@keystone-next/example-roles	Patch
@keystone-next/example-todo	Patch
@keystone-next/auth	Major
@keystone-next/cloudinary	Patch
@keystone-next/fields-document	Patch
@keystone-next/fields	Patch
@keystonejs/test-utils	Patch

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[timleslie]

Looks good 👍