Add Chapter 3 - GraphQL Integration Example

[shpun817]

@billy1624 @tyt2y3 Ready for review.

[billy1624]

I think we should include the link to the full source code of the example at the start of each chapter.

• https://www.sea-ql.org/sea-orm-tutorial/ch01-00-build-backend-getting-started.html
• https://www.sea-ql.org/sea-orm-tutorial/ch02-00-integration-with-rocket.html
• https://www.sea-ql.org/sea-orm-tutorial/ch03-00-integration-with-graphql.html

[billy1624]

Please add our example for chapter 3 to READMD.md

• sea-orm-tutorial/README.md

  Lines 9 to 10 in e53392f

  	1. [**Bakery Backend**](https://www.sea-ql.org/sea-orm-tutorial/ch01-00-build-backend-getting-started.html) - This chapter covers the basics of using SeaORM to interact with the database (a MySQL database is used for illustration). On top of this backend you can build any interface you need.
  	2. [**Rocket Integration**](https://www.sea-ql.org/sea-orm-tutorial/ch02-00-integration-with-rocket.html) - This chapter explains how to integrate the SeaORM backend into the Rocket framework to create a web application that provides a web API or even a simple frontend.

[billy1624]

I think we can add one extra endpoint for debugging / experimental purpose: /graphql served with GET request

The UI is user friendly and easy to play around with GraphQL. Most importantly it provide the schema, query and mutation info.

We add a page to introduce this optional "feature". With a few screen capture (of your own) and showing the schema info panel, query and mutation operations.

Implementation: shpun817/sea-orm-tutorial@master...billy1624:pr/14

[billy1624]

Last but not least, can we stream SeaORM result via GraphQL subscription?

References:

• https://docs.rs/sea-orm/0.8.0/sea_orm/query/struct.Select.html#method.stream
• https://async-graphql.github.io/async-graphql/en/subscription.html
• https://github.com/async-graphql/examples/blob/fa8fc5dde0e1f70dee67719eceecfc9ade250d1f/models/books/src/lib.rs#L127-L136

[billy1624]

Hey @shpun817, all in all it looks great!! :D

[shpun817]

@billy1624 Thanks for the comments!

GraphQL Subscription currently cannot be unsupported by SeaORM, will open an issue for it. (Issue #868)

Otherwise, Chapter 3 is again ready for review!

[billy1624]

Thanks!! @shpun817 Appreciated :D