How to send a timestamp of the current time from ESP32 to Cloud Firestore Database?

[CalColistra]

I have been able to commit String data into an array from the ESP32 to my Cloud Firestore Database. But, I would like to also commit a timestamp to an array of timestamps from the ESP32. Is that possible with this Github library?
My problem is that I can't figure out how to create a timeStamp object that can be passed in the content.set() function. I would really appreciate if anyone could shed some light on this subject.

I get this error message when trying to commit a time stamp:
Commit a document (append array)... Invalid value at 'writes[0].transform.field_transforms[0].append_missing_elements.values[0].timestamp_value' (type.googleapis.com/google.protobuf.Timestamp), Field 'timestampValue', Invalid data type for timestamp, value is 4

[mobizt]

The Firestore REST API does not support this.

The timestamp set to the field is the request timestamp's server value which only available for one transformation type called setToServerValue while append something is the appendMissingElements transformation type which cannot be mixed.

You need to manually append string of your defined timestamp to the field you want to append.

Please note that, the library is the REST API client which you need to read the Google documentation for the feature and application of API.

The library functions descriptions are available in README.md in src folder.