Change in date format for originalTimestamp

[shraddha1313]

Hi Team,
Based on my discussion with @pooyaj, we discovered that the value for originalTimestamp generates the date time string with microseconds instead of milliseconds. This is leading to malformed payloads and Segment is not processing calls with originalTimestamp value having sub-millisecond data in them. All other timestamp keys such as sentAt, timestamp and receivedAt have milliseconds in them.

This behavior was discovered for the Python Server side library 1.4.0 through PyPi. Could you please ensure that we pass milliseconds instead of microseconds for the value of originalTimestamp moving forward?

Example:
malformed value - "originalTimestamp": "2022-07-28T21:43:35.291077+00:00"
corrected value - "originalTimestamp": "2022-08-02T00:43:35.291+00:00"

Please let me know if you have any questions. Thanks!

[MichaelGHSeg]

Addressed by PR #242