Add view for StudyGroups

app/policies/study_group_policy.rb

@@ -0,0 +1,21 @@
+class StudyGroupPolicy < AdminOnlyPolicy
+  def index?
+    admin? || teacher?
+  end
+
+  [:show?, :destroy?, :edit?, :update?].each do |action|
+    define_method(action) { admin? || @user.teacher? && @record.users.include?(@user) }
+  end
+
+  class Scope < Scope
+    def resolve
+      if @user.admin?
+        @scope.all
+      elsif @user.teacher?
+        @scope.joins(:study_group_memberships).where('user_id = ? AND user_type = ?', @user.id, @user.class.name)
+      else
+        @scope.none
+      end
+    end
+  end
+end