Custom replacement of error values

[flymedllva]

Component(s)

router

Is your feature request related to a problem? Please describe.

I have a need for a custom implementation of the message, extensions rewrite of the error. Let's say to configure it through modules. I want to replace message depending on the content in extensions. Also not all my subgraphs substitute extensions correctly, I could bring all the errors to the same format here.

I can do PR if we agree on some implementation

Describe the solution you'd like

I can use values []*fastjson.Value as optionallyOmitErrorExtensions does, or []GraphQLError/subgraphError, which would seem more convenient.

Describe alternatives you've considered

No response

Additional context

No response