Expose access to the SchemaParser dictionary

[givemetheinternet]

I want to suggest an idea and checked that ...

• ... to my best knowledge, my idea wouldn't break something for other users
• ... the documentation does not mention anything about my idea
• ... there are no open or closed issues that are related to my idea

Description

The mapping from graphql schema type to Java implementation type/class is held in a private member variable dictionary within the SchemaParser class. It would be useful to have the information about this mapping easily accessible (though directly immutable) to clients of the API either through the SchemaParser itself, or the GraphQLSchema that gets finally generated.

Use Cases

This change would enable easier unit/integration testing of applications relying on graphql-java-tools to generate schemas from files. For example, a specific test I need to write must verify that the enum options listed in the schema exactly match the enum options available in the related Java type.