type ContextFieldExtractor = func(context.Context) zapcore.Field

const (
   // n.b. This is used in conjunction with the skip field produced by Context() to indicate that
   //      this is a special-cased field, enabling zapfx to detect context fields and subsequently
   //      run any configured ContextFieldExtractors. When used, the corresponding zapcore.Field
   //      looks similar to:
   //
   //          zapcore.Field{
   //            Type:      zapcore.SkipType,
   //            Integer:   _contextFieldIndicator,
   //            Interface: ctx,
   //          }
   _contextFieldIndicator int64 = 1<<8 - 1
 )
    
   // Context wraps ctx as a zapcore.Field, suitable for use with calls to zap.Logger. It may only be
   // used by loggers provided by zapfx; other loggers will panic due to its internal field type.
   //
   // Importantly, Context differs from other zapcore.Field types in that it does not guarantee a 1:1
   // ratio of provided:encoded fields. Specifically, it:
   //
   //   - May not result in an encoded field, in cases in which there are no configured underlying
   //     context extractors or where context baggage does not contain the necessary context keys;
   //   - May result in more than one encoded field, in cases in which multiple context extractors
   //     find keys and produce fields; and
   //   - Does not indicate a concrete field key or value at log time, as key:value pairs of any
   //     resulting field(s) are not known until the configured extractors have run just prior to log
   //     entry encoding.
 func Context(ctx context.Context) zapcore.Field {
     return zapcore.Field{
       Type:      zapcore.SkipType,
       Integer:   _contextFieldIndicator,
       Interface: ctx,
     }
 }

Unfortunately, it never made it to OSS.