Remove static methods from TimeEntriesDao

The class TimeEntriesDao has the following static method:
```
@staticmethod
def current_user_id():
return current_user_id()
```

As you can see, it returns an existing function part of the security.py file. We can use directly that function instead of returning the same function. Please refactor this, we should aim for having 0 static methods. We should use either a POO approach or functions directly. But it does not make any sense to have static methods.