code: @Nonnull
      public ZipkinAnnotationsStore addAnnotation(@Nonnull String key, @Nonnull String value) {
          return addBinaryAnnotation(key, value, defaultEndpoint);
      }
docs: Adds a (binary) string annotation for an event.
  
  @param key   The key of the annotation
  @param value The value of the annotation
  @return this object