Fix: Password storage issue with PostgreSQL backend

[ReeseWang]

Description

This pull request addresses an issue where the password field of the User struct was being stored as an empty string in the PostgreSQL database, while working correctly with the SQLite backend (not sure why). The issue was caused by the custom MarshalJSON and String methods defined on the PrivateString type, which always returned an empty string.

Changes

• Implemented custom Value and Scan methods for the PrivateString type to handle database serialization and deserialization correctly.
  • The Value method returns the actual string as a driver.Value when storing the user record in the database.
  • The Scan method properly assigns the string from the database to the PrivateString field when querying the user record.
• The custom methods ensure that the string is stored in the PostgreSQL database, while still keeping the password/hash hidden in the JSON and string representations of the PrivateString type.

Testing

• Verified that the password field is stored correctly in the PostgreSQL database after applying the changes.
• Local user creation and login work normally.
• Local user login works normally after password changed by admin.

[h44z]

thanks