extendSchema
Produces a new schema given an existing schema and a document which may contain GraphQL type extensions and definitions. The original schema will remain unaltered.
Because a schema represents a graph of references, a schema cannot be extended without effectively making an entire copy. We do not know until it's too late if subgraphs remain unchanged.
This algorithm copies the provided schema, applying extensions while producing the copy. The original schema remains unaltered.
function extendSchema(
schema: GraphQLSchema,
documentAST: DocumentNode,
options?: Options,
): GraphQLSchema;