chore: Create client API conversations with custom attributes (#8040)

- Update client API create conversations endpoint to accept custom attributes as well.

swagger/swagger.json

@@ -847,6 +847,16 @@
         "description": "Create a conversation",
         "security": [
 
+        ],
+        "parameters": [
+          {
+            "name": "data",
+            "in": "body",
+            "required": true,
+            "schema": {
+              "$ref": "#/definitions/public_conversation_create_payload"
+            }
+          }
         ],
         "responses": {
           "200": {
@@ -6617,6 +6627,15 @@
         }
       }
     },
+    "public_conversation_create_payload": {
+      "type": "object",
+      "properties": {
+        "custom_attributes": {
+          "type": "object",
+          "description": "Custom attributes of the conversation"
+        }
+      }
+    },
     "extended_contact": {
       "allOf": [
         {