Add global warning message before nullify the error

Author: tongoss

exporters/otlp/otlplog/otlploggrpc/config.go

@@ -463,6 +463,7 @@ func convHeaders(s string) (map[string]string, error) {
 	}
 	// If at least one valid header exists, reset err to nil
 	if len(out) > 0 {
+		global.Warn("Some headers were invalid but at least one valid header exists: %v", err)
 		err = nil
 	}
 	return out, err

exporters/otlp/otlplog/otlploghttp/config.go

@@ -565,6 +565,7 @@ func convHeaders(s string) (map[string]string, error) {
 	}
 	// If at least one valid header exists, reset err to nil
 	if len(out) > 0 {
+		global.Warn("Some headers were invalid but at least one valid header exists: %v", err)
 		err = nil
 	}
 	return out, err