GraphQL implementation #649
Description
We should think about implementing a GraphQL endpoint /graphql probably using https://github.com/webonyx/graphql-php so that it is possible to query each operation through GraphQL. Since we have the request and response schema of each operation we could generate the fitting GraphQL types. Our resolver would need to call the fitting action and we would need to add a new GraphqlRequestContext which could be used so that actions i.e. only query specific fields.