feat(api): delete workspace groups and record who signed a content event

contracts/api.schemas.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "x-backend-contract-sha256": "655e918f3443073c270bdeb9ae4e69d79dacf83baa90dea1a0cdcfe71d2b8bd5",
+  "x-backend-contract-sha256": "22853abd6c1bf74053682018cd214fecb34c664e4abe043a15c1595566419350",
   "$defs": {
     "AccountChannelBody": {
       "type": "object",
@@ -1616,6 +1616,16 @@
         "signature": {
           "type": "string"
         },
+        "signerAccount": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
         "signerDeviceId": {
           "type": "string"
         },