Can anyone recommend a good Authentication API that integrates well with Swift?

I’ve tried Auth0 (which is what this site seems to be using now), but I’m not crazy about it. I like their web dashboard manager, but documentation and 3rd party integration APIs are outdated; especially the Twitter one. Plus I can’t find anywhere where they offer a simple “logout” method without having to implement a callback URL. I’m thinking about trying out Stormpath, but before I head down that road does anyone have any recommendations? Any first hand experience?

UPDATE: I’m trying out Firebase. If anyone has used it, would love to have your feedback. Once I play around with it for a few days, I’ll post an update on my impression of it.

UPDATE: Um, Firebase… freaking amazing. This is the first time I’ve tried it, and WOW. Once you get the pods installed and updated, this API is powerful. It essentially takes the Apple APIs and pumps them full of steroids. Authentication is a breeze. Adding ads to my app through AdMob took about 1 minute with 4 lines of code. After reviewing the Firebase APIs and everything it offered, I ended up redoing my entire app. I was initially using Auth0 and CloudKit for authentication and database, and was able to recode everything in 2 days using Firebase for authentication, database, ads, and analytics (I guess it really took 3 days, because it took me a day to learn JSON and NoSQL. I had never used them before). One of the most impressive features is the NoSQL database. It updates in realtime, without any manual refreshing. If anyone else has used this, I would love to hear your feedback. Are there any drawbacks of using Firebase that I’m missing?