user: move User into config package

- Add YAML tags for the fields

system/user.go

@@ -6,30 +6,16 @@ import (
 	"os/exec"
 	"os/user"
 	"strings"
+
+	"github.com/coreos/coreos-cloudinit/config"
 )
 
-type User struct {
-	Name                string   `yaml:"name"`
-	PasswordHash        string   `yaml:"passwd"`
-	SSHAuthorizedKeys   []string `yaml:"ssh-authorized-keys"`
-	SSHImportGithubUser string   `yaml:"coreos-ssh-import-github"`
-	SSHImportURL        string   `yaml:"coreos-ssh-import-url"`
-	GECOS               string   `yaml:"gecos"`
-	Homedir             string   `yaml:"homedir"`
-	NoCreateHome        bool     `yaml:"no-create-home"`
-	PrimaryGroup        string   `yaml:"primary-group"`
-	Groups              []string `yaml:"groups"`
-	NoUserGroup         bool     `yaml:"no-user-group"`
-	System              bool     `yaml:"system"`
-	NoLogInit           bool     `yaml:"no-log-init"`
-}
-
-func UserExists(u *User) bool {
+func UserExists(u *config.User) bool {
 	_, err := user.Lookup(u.Name)
 	return err == nil
 }
 
-func CreateUser(u *User) error {
+func CreateUser(u *config.User) error {
 	args := []string{}
 
 	if u.PasswordHash != "" {