fix(systemd): include service user in service file generation

* Add ServiceUser field to Config struct for user specification.
* Update Generate and Install functions to accept service user.
* Modify tests to reflect changes in service user handling.

config/config.go

@@ -3,6 +3,7 @@ package config
 import (
 	"fmt"
 	"os"
+	"os/user"
 	"path/filepath"
 
 	"gopkg.in/yaml.v3"
@@ -24,9 +25,21 @@ type Unit struct {
 
 // Config is the root config structure.
 type Config struct {
-	Units  []Unit `yaml:"units"`
-	Prefix string `yaml:"prefix,omitempty"` // prepended to generated service name, e.g. "prod-"
-	Suffix string `yaml:"suffix,omitempty"` // appended to generated service name, e.g. "-svc"
+	Units       []Unit `yaml:"units"`
+	Prefix      string `yaml:"prefix,omitempty"`       // prepended to generated service name, e.g. "prod-"
+	Suffix      string `yaml:"suffix,omitempty"`       // appended to generated service name, e.g. "-svc"
+	ServiceUser string `yaml:"service_user,omitempty"` // User= in [Service] section; defaults to "unitdore"
+}
+
+// EffectiveServiceUser returns the configured service user, or the current OS user if unset.
+func (c *Config) EffectiveServiceUser() string {
+	if c.ServiceUser != "" {
+		return c.ServiceUser
+	}
+	if u, err := user.Current(); err == nil {
+		return u.Username
+	}
+	return "root"
 }
 
 // Load reads and parses the config file at path.