Add error section in custom attributes configuration

[bnjjj]

What is missing in our implementation for custom attributes and could be useful is to add an error subsection to reflect the same behavior we have in our plugin hooks. For example instead of having:

telemetry:
  metrics:
    prometheus:
      enabled: true
    common:
      attributes:
        subgraph:
          all:
            response:
              body:
              - path: .errors[0].extensions.type
                name: subgraph_error_extended_type

we could have :

telemetry:
  metrics:
    prometheus:
      enabled: true
    common:
      attributes:
        subgraph:
          all:
            errors: # Only works if it's a valid GraphQL error
              include_messages: true # Will include the error message in a message attribute
              include_locations: true
              include_paths: true
              extensions: # Include extension data
                - name: subgraph_error_extended_type # Name of the attribute
                  path: .type # JSON query path to fetch data from extensions

Originally posted by @bnjjj in #1198 (comment)

[BrynCooke]

Q: Will the user be able to specify more than one error section? If not then error->errors.

Is there a possibility that users will want to filter only on certain paths of error. Not saying that this is a requirement, just posing the question.

[bnjjj]

No only one error. It's already written error BTW. About the filtering on specific path we could provide a path /here/is/my/path instead of just provide a bool. That could be a feature

[BrynCooke]

So if there's only one error section, then it should be called errors as it applies to many errors.
include_message and include_path should also be plural.

[bnjjj]

Updated ! Thanks :)

[BrynCooke]

just checking: extensions is an array? If so the example yaml needs a dash.

[bnjjj]

Ok after some investigations we don't fill the path and locations field when we have an error in the subgraph http request. So for now I will omit these fields and do not add the ability to include them.
Final version:

telemetry:
  metrics:
    prometheus:
      enabled: true
    common:
      attributes:
        subgraph:
          all:
            errors: # Only works if it's a valid GraphQL error
              include_messages: true # Will include the error message in a message attribute
              extensions: # Include extension data
                - name: subgraph_error_extended_type # Name of the attribute
                  path: .type # JSON query path to fetch data from extensions