Problem

This PR is part of a greater effort to improve the documentation on the Admin part of the API Platform framework.
This PR will serve as a reference for code examples and screenshots featured in an upcoming PR to the documentation repo (api-platform/docs#2141).

Currently, the example Admin Apps in the Storybook are very basic, and do not allow to grasp the power of API Platform + React Admin.

Solution

This PR adds the following:

• New Book and Review entities, that leverage validation, realtime, relationship, ordering, filtering and default representation
• A new story called UsingGuessers that shows the customization made possible by only leveraging the API Platform Admin Components (i.e. the Guessers)
• A new story called AdvancedCustomization that shows the customization made possible by also leveraging React Admin Components

How to test

1. Run the Storybook: docker compose up
2. Accept self-signed certificate by browsing https://localhost
3. Play with the Basic story: http://localhost:3000/?path=/story/admin-basic--admin
4. Play with the UsingGuessers story: http://localhost:3000/?path=/story/admin-custom-usingguessers--using-guessers
5. Play with the AdvancedCustomization story: http://localhost:3000/?path=/story/admin-custom-advancedcustomization--advanced-customization

Screenshots