fmt.Stringer support for user attributes (especially for SQL query parameters)

[siketyan]

Summary

User attributes in segments does not support types other than primitive types.

go-agent/v3/newrelic/attributes_from_internal.go

Lines 357 to 374 in 0100f62

	switch v := val.(type) {
	case string, bool,
	uint8, uint16, uint32, uint64, int8, int16, int32, int64,
	uint, int, uintptr:
	case float32:
	if err := validateFloat(float64(v), key); err != nil {
	return nil, err
	}
	case float64:
	if err := validateFloat(v, key); err != nil {
	return nil, err
	}
	default:
	return nil, errInvalidAttributeType{
	key: key,
	val: val,
	}
	}

I am using the pgx tracer from nrpgx5 package, the querying segment cannot be sent successfully because some of the query parameters are not primitive:

unable to end datastore segment collection=user operation=select product=Postgres reason="attribute '$1' value of type uuid.UUID is invalid"

uuid.UUID are not primitive, but it implements fmt.Stringer interface.
It would be great if we can handle fmt.Stringer for attributes.

Desired Behaviour

Attributes on a segment accept fmt.Stringer implemented types.

Possible Solution

Add a case to the switch statement:

case fmt.Stringer:
    val = val.String()

Additional context

N/A