Fixes NotNullViolation on user creation

[mvilanova]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the Pydantic user models to prevent null values for the password field and avoid database NotNullViolation errors on user creation.

• Changed UserLogin.password from optional (str | None = None) to a required str.
• Adjusted UserRegister.password to default to an empty string instead of None.

Comments suppressed due to low confidence (1)

src/dispatch/auth/models.py:168

• Add tests for missing or empty password on login and registration to verify that the custom validator raises the expected error and prevents null or empty values.

    password: str