add subjects and reviwers query

app/graphql/resolvers/reviewers_query_resolver.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+module Resolvers
+  class ReviewersQueryResolver
+    def initialize(context)
+      @context = context
+    end
+
+    def resolve
+      UserPolicy::Scope.new(@context[:current_user], User)
+        .resolve
+        .joins(:roles)
+        .where(roles: { name: %i[teacher nde] })
+        .where.not(id: @context[:current_user].id)
+        .distinct
+    end
+  end
+end