web&server: show raw body contents of UnhandledContentType

web/graphql/schema.json

@@ -1505,6 +1505,22 @@
                   "ofType": null
                 }
               }
+            },
+            {
+              "args": [],
+              "deprecationReason": null,
+              "description": null,
+              "isDeprecated": false,
+              "name": "contentTree",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "String",
+                  "ofType": null
+                }
+              }
             }
           ],
           "inputFields": null,

web/graphql/show_thread.graphql

@@ -23,6 +23,7 @@ query ShowThreadQuery($threadId: String!) {
         __typename
         ... on UnhandledContentType {
           contents
+          contentTree
         }
         ... on PlainText {
           contents