This member is added by an implicit conversion from ServiceCallHolder to
any2stringadd[ServiceCallHolder] performed by method any2stringadd in scala.Predef.
This member is added by an implicit conversion from ServiceCallHolder to
StringFormat[ServiceCallHolder] performed by method StringFormat in scala.Predef.
Holds the service call itself.
The implementations of this are intentionally opaque, as the mechanics of how the service call implementation gets passed around is internal to Lagom.