Feature: Option to ignore duplicate Message-IDs

This option (default off) silently ignores any new messages with duplicate Message-IDs. This update includes a new database structure and automatic rebuild of existing data.

server/ui/api/v1/swagger.json

@@ -655,6 +655,10 @@
             "$ref": "#/definitions/Attachment"
           }
         },
+        "MessageID": {
+          "description": "Message ID",
+          "type": "string"
+        },
         "Read": {
           "description": "Read status",
           "type": "boolean"