This member is added by an implicit conversion from Content-Encoding to
any2stringadd[Content-Encoding] performed by method any2stringadd in scala.Predef.
This member is added by an implicit conversion from Content-Encoding to
StringFormat[Content-Encoding] performed by method StringFormat in scala.Predef.
RFC 7231 section 3.1.2.2
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding