* Add basic implementation for the graphql extension service
* Add createPolicyContext in @strapi/utils
* policiesMiddleware implementation for graphql
* wrapResolvers first implementation (authentication, middlewares, policies)
* move the content API schema build from /generators to /content-api. Extract types' register functions into a dedicated folder
* fix schema generation on bootstrap
* update the graphql service file to match new services arch
* fix single type queries
* simplify entity's resolver
* use apollo graphql conventions for resolver's args naming
* use the graphql extension system in i18n to add a locale arg to localized queries & mutations
