message: Fix event mapping and add a missing field
diff: }
  },
  "AcsChatParticipantAddedToThreadEventData": {
  - "description": "Schema of the Data property of an EventGridEvent for an Microsoft.Communication.ChatParticipantAddedToThread event.",
  + "description": "Schema of the Data property of an EventGridEvent for an Microsoft.Communication.ChatThreadParticipantAdded event.",
  "allOf": [
  {
  "$ref": "#/definitions/AcsChatEventInThreadBaseProperties"
  }
  },
  "AcsChatParticipantRemovedFromThreadEventData": {
  - "description": "Schema of the Data property of an EventGridEvent for an Microsoft.Communication.ChatParticipantRemovedFromThread event.",
  + "description": "Schema of the Data property of an EventGridEvent for an Microsoft.Communication.ChatThreadParticipantRemoved event.",
  "allOf": [
  {
  "$ref": "#/definitions/AcsChatEventInThreadBaseProperties"
  "description": "Schema of common properties of all thread-level chat events",
  "type": "object",
  "properties": {
  + "transactionId": {
  + "description": "The transaction id will be used as co-relation vector",
  + "type": "string"
  + },
  "threadId": {
  "description": "The chat thread id",
  "type": "string"
  