Allow custom SSH user in UI for built-in SSH server (#2617) (#2678)

* Allow custom SSH user in UI for built-in SSH server (#2617)

* Some fixes

* Did make fmt

* Updated according to review

- Renamed config to BUILTIN_SSH_SERVER_USER
- Removed unnecessary default string value for config item

* Updated according to review

* Fixed some minor issues

modules/setting/setting.go

@@ -90,6 +90,7 @@ var (
 	SSH = struct {
 		Disabled             bool           `ini:"DISABLE_SSH"`
 		StartBuiltinServer   bool           `ini:"START_SSH_SERVER"`
+		BuiltinServerUser    string         `ini:"BUILTIN_SSH_SERVER_USER"`
 		Domain               string         `ini:"SSH_DOMAIN"`
 		Port                 int            `ini:"SSH_PORT"`
 		ListenHost           string         `ini:"SSH_LISTEN_HOST"`
@@ -915,6 +916,8 @@ func NewContext() {
 		}
 	}
 
+	SSH.BuiltinServerUser = Cfg.Section("server").Key("BUILTIN_SSH_SERVER_USER").MustString(RunUser)
+
 	// Determine and create root git repository path.
 	sec = Cfg.Section("repository")
 	Repository.DisableHTTPGit = sec.Key("DISABLE_HTTP_GIT").MustBool()