Issue #110: update book tutorial

[Howriq]

No description provided.

[alexmerlin]

To be continued...

[alexmerlin]

1. In ReleaseDateInput, replace:
   'message' => sprintf(Message::INVALID_VALUE, 'releaseDate'),
   with:
   'message' => Message::INVALID_VALUE,
   and remove use function sprintf;.

2. The migrations diff command is outdated, replace it with:

php ./vendor/bin/doctrine-migrations diff

3. The path mentioned in this sentence has changed in 6.0:

This will check for differences between your entities and database structure and create migration files if necessary, in data/doctrine/migrations.

Version 6.0 stores migrations in the Core module under the following path:
src/Core/src/App/src/Migration

4. The migrations run command should also be updated:

php ./vendor/bin/doctrine-migrations migrate

5. Rename across the document GetBookHandler to GetBookResourceHandler

6. Rename across the document PostBookHandler to PostBookResourceHandler

so that they follow our naming convention.

[alexmerlin]

After this, these steps will have to be tested in version 6.0 of Dotkernel API.

[alexmerlin]

1. Format the contents of Book->getArrayCopy
2. Replace the To retrieve a book use: section with:

To retrieve a book, curl one of the links found in the output of the list books command, under _embedded . books . * . _links . self . href