fix: explicity set updated_at field when updating identity

[maoanran]

Problem

The updated_at field in the identities table is not being updated when an identity's traits are modified. This is unexpected behavior because the pop library should automatically update the updated_at field when a record is modified.

However, in the current implementation, the identity is being saved with the old updated_at timestamp, which causes the pop library to skip updating this field. As a result, the updated_at field does not reflect recent changes, which can lead to issues with auditing, synchronization, or downstream systems relying on the correct timestamps for updated data.

Cause

The issue arises because the existing code inadvertently preserves the previous updated_at value during the update operation. When saving the identity, the pop library sees that the field is already set and, as a result, does not overwrite it with the current timestamp.

Solution

This PR explicitly sets the updated_at field when updating an identity. By ensuring the field is updated within the code, we force the correct behavior, even if the underlying pop library does not update the field automatically.

Steps to manually reproduce:

1. Update the traits of a user.
2. Check the updated_at field in the identities table to confirm that it reflects the recent update.

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  [email protected]) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[CLAassistant]

All committers have signed the CLA.

[aeneasr]

Makes sense!