[scala][client]: scala-http4s: minor improvement (enum companion method, remove implicit, error handling) #833

Job	Run time
Build sbt/Scala client, servers (samples/client/petstore/java/okhttp-gson)	36s
Build sbt/Scala client, servers (samples/client/petstore/scalaz)	2m 13s
Build sbt/Scala client, servers (samples/client/petstore/scala-pekko)	44s
Build sbt/Scala client, servers (samples/client/petstore/scala-http4s)	39s
Build sbt/Scala client, servers (samples/server/petstore/scala-lagom-server)	3m 54s
Build sbt/Scala client, servers (samples/server/petstore/scala-play-server)	6m 1s
Build sbt/Scala client, servers (samples/server/petstore/scala-akka-http-server)	2m 4s
Build sbt/Scala client, servers (samples/server/petstore/scala-pekko-http-server)	42s
Build sbt/Scala client, servers (samples/server/petstore/scalatra)	2m 54s
Build sbt/Scala client, servers (samples/server/petstore/scala-finch)	3m 14s
Build sbt/Scala client, servers (samples/server/petstore/scala-http4s-server)	50s
Build sbt/Scala client, servers (samples/server/petstore/scala-cask)	1m 3s
	24m 54s

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