Hide errors stacktrace

[eaceto]

Is your feature request related to a problem? Please describe.
When a GraphQL error appears a complete description of the error is sent, which include stack trace information in most cases.

Describe the solution you'd like

Example error

{
   "errors":[
      {
         "message":"Variable \"$person\" got invalid value \"lukesk\"; Value \"lukesk\" does not exist in \"StarWarsPeople\" enum.",
         "extensions":{
            "code":"BAD_USER_INPUT",
            "exception":{
               "stacktrace":[
                  "GraphQLError: Variable \"$person\" got invalid value \"lukesk\"; Value \"lukesk\" does not exist in \"StarWarsPeople\" enum.",
                  "    at /usr/src/app/node_modules/graphql/execution/values.js:116:15",
                  "    at coerceInputValueImpl (/usr/src/app/node_modules/graphql/utilities/coerceInputValue.js:131:9)",
                  "    at coerceInputValueImpl (/usr/src/app/node_modules/graphql/utilities/coerceInputValue.js:54:14)",
                  "    at coerceInputValue (/usr/src/app/node_modules/graphql/utilities/coerceInputValue.js:37:10)",
                  "    at _loop (/usr/src/app/node_modules/graphql/execution/values.js:109:69)",
                  "    at coerceVariableValues (/usr/src/app/node_modules/graphql/execution/values.js:121:16)",
                  "    at getVariableValues (/usr/src/app/node_modules/graphql/execution/values.js:50:19)",
                  "    at buildExecutionContext (/usr/src/app/node_modules/graphql/execution/execute.js:203:61)",
                  "    at executeImpl (/usr/src/app/node_modules/graphql/execution/execute.js:101:20)",
                  "    at execute (/usr/src/app/node_modules/graphql/execution/execute.js:60:35)"
               ]
            }
         }
      }
   ]
}

We should give the possibility to hide (stop propagating) errors[].extensions.exception , for example, by setting the following properties in the configuration yaml:

routes:
    - http:
          uri: '/films/{film}'
          method: GET
      graphql:
          endpoint: 'https://swapi.skyra.pw/'
          query: |
              {
                  getFilm(film: $film) {
                      title
                      releaseDate
                      producers
                      episodeId
                  }
              }
          types:
            film: Float
          errors:
            hidePath: true # defaults to false
            hideLocations: true # defaults to false
            extensions:
               hide: true     # defaults to false. True hides the complete **extensions** dictionary
               codeMapping:
                  BAD_USER_INPUT:  400     # Maps **extensions.code** to HTTP Status. Error "BAD_USER_INPUT" maps to Status Code 400 (Bad Request)