Core: [GraphQL] Custom errors for graphql endpoint

[mahmoodbazdar]

In GraphQL php library that Api platform is using it user can define custom error format.
Here is documentation for custom errors in php GraphQL library:
https://webonyx.github.io/graphql-php/error-handling/#custom-error-handling-and-formatting

I think we should add this feature so developers can create their own error formats based on exceptions.

Example 1: We don't have status codes for errors and I think its helps if we return a status property in error object so frontend developer can decide how to show it .

Example 2: Validation errors format isn't good now. All of error massages concat in one string and frontend developer needs to do some process on error string on every error messages.

[alanpoulain]

Having a way to customize the errors would be indeed a nice improvement.

[mahmoodbazdar]

I'll try to create pull request for it.

[lukasluecke]

This is actually a pretty important issue, since right now errors get completely swallowed in production environments, and there's no easy way to handle them (at least I didn't find one).

I have temporarily overridden the api_platform.graphql.executor service, and added my error handling logic there - for anyone that needs a quick solution 🙂