Fix Contractor last_updated not being set

[PrenSJ2]

Technical Description

when validating ContractorModel in validation.py, we set last_updated (datetime). The problem is TC2 was not sending alast_updated field.

This is solved by using the requested_timestamp send by TC2 instead

Recreation steps

• follow readme to setup in Improve Readme + Logfire #554
• Setup socket-frontend too Improve Readme socket-frontend#357
• once your socket integration in TC2 is connected, take your public key and set it in the socket-frontend public.html
• in TC2, enable public tutor profiles
• add the public profile label to 4 tutors
• Settings > Approve Public Tutor Profiles
• see the order of the contractors not move ( in the socket-frontend)

Testing

• do above
• see contractors move depending on last updated