A GraphQL Schema defines the capabilities of a GraphQL server. It exposes all available types and directives on the server, as well as the entry points for query, mutation, and subscription operations.
- description
 - types[__Type!]!A list of all types supported by this server.
 - queryType__Type!The type that query operations will be rooted at.
 - mutationType__TypeIf this server supports mutation, the type that mutation operations will be rooted at.
 - subscriptionType__TypeIf this server support subscription, the type that subscription operations will be rooted at.
 - directives[__Directive!]!A list of all directives supported by this server.