refactor: remove utils pkg

BREAKING CHANGE: utils package has been removed in favor of specific new
packages (http, crypto, strings)

example/client/app/app.go

@@ -12,8 +12,8 @@ import (
 	"github.com/sirupsen/logrus"
 
 	"github.com/caos/oidc/pkg/client/rp"
+	httphelper "github.com/caos/oidc/pkg/http"
 	"github.com/caos/oidc/pkg/oidc"
-	"github.com/caos/oidc/pkg/utils"
 )
 
 var (
@@ -30,7 +30,7 @@ func main() {
 	scopes := strings.Split(os.Getenv("SCOPES"), " ")
 
 	redirectURI := fmt.Sprintf("http://localhost:%v%v", port, callbackPath)
-	cookieHandler := utils.NewCookieHandler(key, key, utils.WithUnsecure())
+	cookieHandler := httphelper.NewCookieHandler(key, key, httphelper.WithUnsecure())
 
 	options := []rp.Option{
 		rp.WithCookieHandler(cookieHandler),