plenty of changes to make the package more ergonomic

Including: bug fixes, api changes, new packages, and more!

pkg/exporters/gelf_exporter/trace.go

@@ -78,7 +78,7 @@ func (e *Exporter) ExportSpans(ctx context.Context, spans []trace.ReadOnlySpan)
 				ExtraFields: attributes,
 			}
 			for _, attrKV := range event.Attributes {
-				if attrKV.Key == "long_message" {
+				if attrKV.Key == attr.LogMessageLongKey {
 					gelf.LongMessage = attrKV.Value.AsString()
 					continue
 				}