This commit introduces multiple test cases for the User model, covering creation, updating, deletion, unique constraints, required fields, default values, string representation, and handling of complex JSON preferences. These tests help ensure the model behaves as
Simplify database module by re-organizing engine creation, session handling, and removing redundant methods. Introduce SQLite compatibility for testing and add a utility module for test database setup and teardown. Integrate initial unit tests for user models and update dependencies for security and testing.
