Support functions in schema security key.

[Pavel910]

Related Issue

CMS schema supports addition of typeDefs and resolvers via plugins. However, we must also be able to add security rules via plugins. At this point security only supported an object as its value, and as such it was interpreted too early for other plugins to be registered.

Your solution

This PR adds the ability to assign a function to schema plugin security key, and it will be executed at runtime, when all plugins have already been registered, and so we'll be able to use our plugin system to add graphql-shield rules.

{
  // ... other schema keys
  security: () =>
    merge(
      {
        shield: {
          CmsQuery: {
            getMenu: hasScope("cms:menu:crud")
          },
          CmsMutation: {
            createMenu: hasScope("cms:menu:crud")
          }
        }
      },
      // Fetch plugins and merge with current security value
      ...getPlugins("cms-schema").map(pl => pl.security)
    );
}

How Has This Been Tested?

Manual testing.