[WOC] add unit tests and opt express_pg_sequelize template

[priyansh-narang2308]

description

This pr fix issue #29 by adding basic testing and small architecture improvments to the express_pg_sequelize template.

key changes

• use jest db mocking so api tests run fast without postgres running.
• export express app and wrap app.listen to avoid port issue while testing.
• add jest and supertest with a simple npm test script.
• tests added: cover root route and db routes, incl error cases.

how to test

1. qse init -t express_pg_sequelize -n test-app
2. cd test-app
3. npm install
4. npm test

[Devpool-soc]

Hey @priyansh-narang2308! Thank you for opening a pull request. Make sure to tag the maintainers and link the issue you are solving in your pull-request description if you have not already and they'll review as soon as possible.

[priyansh-narang2308]

It had an error in testing which fixed

[Ashrockzzz2003]

rename to be same as the original js file - index.test.js - it'll improve readability

[priyansh-narang2308]

Made the changes @Ashrockzzz2003