BSON: throw json.exception.out_of_range.409 in case a key to be serialized to BSON contains a U+0000

include/nlohmann/detail/exceptions.hpp

@@ -266,6 +266,7 @@ json.exception.out_of_range.405 | JSON pointer has no parent | The JSON Patch op
 json.exception.out_of_range.406 | number overflow parsing '10E1000' | A parsed number could not be stored as without changing it to NaN or INF.
 json.exception.out_of_range.407 | number overflow serializing '9223372036854775808' | UBJSON and BSON only support integer numbers up to 9223372036854775807. |
 json.exception.out_of_range.408 | excessive array size: 8658170730974374167 | The size (following `#`) of an UBJSON array or object exceeds the maximal capacity. |
+json.exception.out_of_range.409 | BSON key cannot contain code point U+0000 | Key identifiers to be serialized to BSON cannot contain code point U+0000, since the key is stored as zero-terminated c-string |
 
 @liveexample{The following code shows how an `out_of_range` exception can be
 caught.,out_of_range}