Add a `__del__` or `__exit__` method

I'm wondering if it would be worth it to custom-write a method that closes all potential connections to the database during garbage collection (__del__) or after execution in a context manager (__exit__).

They both would have a calling syntax similar to:

def __del__(self):
    self.close_connection()

This way we avoid dangling connections.

pepkit / pepdbagent

Add a `del` or `exit` method #30

pepkit / pepdbagent

Add a `__del__` or `__exit__` method #30

Add a `del` or `exit` method #30