Add Entity Relationship Diagram for Runner

Author: chao-xian

diagrams/runner-erd.mmd

@@ -0,0 +1,11 @@
+classDiagram
+	direction RL
+	class `Submission`
+	`Submission` : +jsonb answers
+	`Submission` : +jsonb form_document
+	`Submission` : +integer form_id
+	`Submission` : +string mail_message_id
+	`Submission` : +string mail_status
+	`Submission` : +string mode
+	`Submission` : +string reference
+	`Submission` : +datetime sent_at