Implement autogenerated mocks for GraphQL API from schema

https://www.graphql-tools.com/docs/mocking#addmockstoschema

> [Mocking](https://www.graphql-tools.com/docs/mocking#mocking)
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> The strongly-typed nature of a GraphQL API lends itself extremely well to mocking. This is an important part of a GraphQL-First development process, because it enables frontend developers to build out UI components and features without having to wait for a backend implementation.
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> Even with a backend that is already built, mocking allows you to test your UI without waiting on slow database requests or building out a component harness with a tool like React Storybook.
> Default mock [example](https://www.graphql-tools.com/docs/mocking#default-mock-example)
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> Let's take a look at how we can mock a GraphQL schema with just one line of code, using the default mocking logic you get out of the box with graphql-tools.
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> To start, let's grab the schema definition string from the makeExecutableSchema example [in the "Generating a schema" article](https://www.graphql-tools.com/docs/generate-schema/#example).