fix(migrations): Set user password_digest only if it was received

[danimo]

This fixes situations where after a migration from v2 due to a peculiar behavior, which refuses empty passwords but not empty password hashes, could end up with an empty password.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.4% Duplication on New Code

See analysis details on SonarCloud

[danimo]

Can you please merge this? it's still security relevant.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud