add rails erd

lib/tasks/auto_generate_diagram.rake

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+# NOTE: only doing this in development as some production environments (Heroku)
+# NOTE: are sensitive to local FS writes, and besides -- it's just not proper
+# NOTE: to have a dev-mode tool do its thing in production.
+if Rails.env.development?
+  RailsERD.load_tasks
+end