Show additional error details when an rpc fails

[fdfzcq]

Fixes the following issue:

If an error is returned with additional details together with code and message, grpcurl will format it poorly and not show the additional details.

[ghost]

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[fdfzcq]

Hello @dragonsinth could you have a look at this small PR when you have time? Thank you!

[dragonsinth]

What's going on here?

[erikjoh]

To give some extra context, we are trying to adopt the richer error model of grpc but grpcurl currently outputs the errors like this:

ERROR:
  Code: InvalidArgument
  Message: Request contains invalid fields
  Details:
  1)	{"@error":"google.rpc.BadRequest is not recognized; see @value for raw binary message data","@type":"type.googleapis.com/google.rpc.BadRequest","@value":"CiQKCnN0cmluZ19vbmUSFk5vIGVtcHR5IHZhbHVlIGFsbG93ZWQKJAoKc3RyaW5nX3R3bxIWTm8gZW1wdHkgdmFsdWUgYWxsb3dlZA=="}

The problem with the current code here is that when using service reflection to resolve google.rpc.BadRequest, it doesn't work since google.rpc.BadRequest doesn't have any protobuf extension.
You can see here that r.source.AllExtensionsForType(mname) returns an err github.com/jhump/protoreflect/grpcreflect.elementNotFoundError which then aborts the formatting.

With the change in this PR, the elementNotFoundError will be ignored and the formatting of the error will successfully be processed and printed:

ERROR:
  Code: InvalidArgument
  Message: Request contains invalid fields
  Details:
  1)	{
    	  "@type": "type.googleapis.com/google.rpc.BadRequest",
    	  "field_violations": [
    	    {
    	      "field": "string_one",
    	      "description": "No empty value allowed"
    	    },
    	    {
    	      "field": "string_two",
    	      "description": "No empty value allowed"
    	    }
    	  ]
    	}

This new code should add extensions (i.e. r.er.AddExtension(exts...)) only if extensions could be found with r.source.AllExtensionsForType(mname).

[dragonsinth]

Gotcha, that makes sense. Why not also ignore the error from r.er.AddExtension(exts...)?

[dragonsinth]

@jhump this seems reasonable to me, WDYT?

[jhump]

Yep, this PR LGTM.

[fdfzcq]

Hello @dragonsinth @jhump can we have this PR merged? :) thx!

[fdfzcq]

@dragonsinth thank you for merging the PR, could you make a new release too? :)