Change initial TrustModel to committer (#18335)

routers/install/install.go

@@ -464,6 +464,8 @@ func SubmitInstall(ctx *context.Context) {
 	cfg.Section("log").Key("ROOT_PATH").SetValue(form.LogRootPath)
 	cfg.Section("log").Key("ROUTER").SetValue("console")
 
+	cfg.Section("repository.signing").Key("DEFAULT_TRUST_MODEL").SetValue("committer")
+
 	cfg.Section("security").Key("INSTALL_LOCK").SetValue("true")
 
 	var internalToken string