healthcheck endpoint (#998)

Co-authored-by: Igor Rzegocki <igor@rzegocki.pl>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/998
Reviewed-by: konrad <k@knt.li>
Co-authored-by: ajgon <vikunja-gitea@ajgon.ovh>
Co-committed-by: ajgon <vikunja-gitea@ajgon.ovh>

pkg/routes/routes.go

@@ -198,6 +198,9 @@ func RegisterRoutes(e *echo.Echo) {
 		registerCalDavRoutes(c)
 	}
 
+	// healthcheck
+	e.GET("/health", HealthcheckHandler)
+
 	// CORS_SHIT
 	if config.CorsEnable.GetBool() {
 		e.Use(middleware.CORSWithConfig(middleware.CORSConfig{