Add privacy control to user profiles

app/controllers/api/v1/users_controller.rb

@@ -63,6 +63,7 @@ module Api
                     .where(name_quality)
                     .where(user_quality)
                     .where(original)
+                    .where(privacy)
                     .order(created_at: :desc)
                     .paginate(page: request.params[:page], per_page: COLLECTION_PER_PAGE)
                     .each do |party|
@@ -176,6 +177,12 @@ params['charge_attack'].to_i
         "name NOT IN (#{joined_names})"
       end
 
+      def privacy
+        return if admin_mode
+
+        'visibility = 1' if current_user != @user
+      end
+
       # Specify whitelisted properties that can be modified.
       def set
         @user = User.find_by('lower(username) = ?', params[:id].downcase)