Add missing license header

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

Author: gearnode

unit/otel_error_handler.go

@@ -1,3 +1,19 @@
+// Copyright (c) 2024 Bryan Frimin <bryan@frimin.fr>.
+//
+// Permission to use, copy, modify, and/or distribute this software
+// for any purpose with or without fee is hereby granted, provided
+// that the above copyright notice and this permission notice appear
+// in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+// WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+// AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+// CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+// OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+// NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
 package unit
 
 import (