Inherited from Serializable
Inherited by implicit conversion any2stringadd from
ETag to any2stringadd[ETag]
Inherited by implicit conversion StringFormat from
ETag to StringFormat[ETag]
Inherited by implicit conversion Ensuring from
ETag to Ensuring[ETag]
Inherited by implicit conversion ArrowAssoc from
ETag to ArrowAssoc[ETag]
RFC 7231 section 2.3
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag