Allow context to be scoped

[ruudk]

By implementing the ScopedContext interface on your context object, you can ensure that
scope is only passed downwards and not shared with other fields.

Example:

query {
  a {
    b {
      c
    }
    d {
      e {
        f
      }
    }
  }
  g {
    h {
      i
    }
  }
}

In the above situation, the following will happen:

• a receives the cloned context from the executor
• b receives the cloned context from a
• c receives the cloned context from b
• d receives the cloned context from a
• e receives the cloned context from d
• f receives the cloned context from e
• g receives the cloned context from the executor
• h receives the cloned context from g
• i receives the cloned context from h

References:

• Scoped Context graphql/graphql-js#2692
• Adds scoped context for propagating values specific to a field and its children rmosolgo/graphql-ruby#2634

[SavageTiger]

That was fast 🚀

[ruudk]

@spawnia The PR is ready for review. I'd love to hear what you think. If you have suggestions on how to improve this, please let me know

[spawnia]

Let's figure out where this can be documented. I think at least the PHPDoc that describes $contextValue should be extended, perhaps an entire new section of docs can be added?

[ruudk]

@spawnia Ready. Added a few lines to the documentation. I think it's sufficient.

[spawnia]

Concerning docs, I would like to provide an example. The pull request description does not seem right:

d receives the cloned context from d
f receives the cloned context from d

Again, I think the following is still true:

I think at least the PHPDoc that describes $contextValue should be extended,

See

graphql-php/src/GraphQL.php

Lines 47 to 51 in 01d7b25

	* contextValue:
	* The context value is provided as an argument to resolver functions after
	* field arguments. It is used to pass shared information useful at any point
	* during executing this query, for example the currently logged in user and
	* connections to databases or other services.

. A more detailed description can be available in the interface. Also, the interface should be added to the class reference generation.

[ruudk]

@spawnia Updated the PR. If you have better wording, please let me know.

[ruudk]

@spawnia Thanks for merging it, would love to have it tagged if you have time 🙏 💙

nvm: I see the PR already.