add checkActionVisibility option

[icebob]

The new checkActionVisibility: true mixin option enables to service to check the visibility property of actions and only generate graphql query/mutations if visibility: null or visibility: "published" (same as in moleculer-web).

Example

module.exports = {
    name: "api",

    mixins: [
        // Gateway
        ApiGateway,

        // GraphQL Apollo Server
        ApolloService({
            routeOptions: {},
            serverOptions: {},
    
            // Enable visibility check
            checkActionVisibility: true
        })
    ]
};