Update SQLAlchemy example to include non-admin and connection refresh logic

[mitchell-elholm]

Description of changes:

Adds non-admin logic and connection token refresh

• Adds a listener for non-admin, and updates the search path to myschema.
• Adds a listener to set a new token every time a connection is created. The connection is created immediately after the parameter is updated.
• Connection refresh can be tested by setting the token expiry to 2 seconds, and then setting a parameter pool_recycle to 1 second in the engine creation. This ensures that it will attempt to open a new connection every second, and that the first token created will not be valid anymore after 1 second. It should succeed, as it created a new token each time it connected. I also tested the negative case, by removing the listener altogether and using a single token with a short timeout, to prove that it would have failed without the token refresh.

engine = create_engine(
        url, 
        connect_args={"sslmode": "verify-full", "sslrootcert": "system"},
        pool_recycle=1 
    )
...

return client.generate_db_connect_admin_auth_token(cluster_endpoint, region, 1)

• Other minor changes: Adds table drop to allow repeated execution.
• Removed SDK, added import

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT-0 license.

Thank you for your contribution!

[trstephen-amazon]

🚢

[trstephen-amazon]

TIL