// method - 1
	let newKey = admin.database().ref().child(`/users/${uid}/stickers/catalog`).push().key;
	let updates = {};
	updates[`/users/${uid}/stickers/catalog/${newKey}`] = {
		state: 'not ready',
		timestamp: (new Date()).toISOString()
	}
	return admin.database().ref().update(updates).then(ret => {

	})

// method - 2
	let newCatalogItem = admin.database().ref().child(`/users/${uid}/stickers/catalog`).push()
	newCatalogItem.set({
		state: 'wow',
		timestamp: (new Date()).toISOString()
	}).then(_ => {
		let path = newCatalogItem.toString();
		console.log('path: ', path);
	})