Congrats on the app, looks very promising. I started with it last night adding a full set of tests, but probably won't go much further. I've read several posts below and understand the feedback you've given to several about using the social media logins. I understand it needs easy administration and I am very likely still in the minority, but this is the first app I've ever used a social medial login with, I broke my rule because I wanted to see and thought it might be worth it. I don't like and trust what gets shared, this is not on you, but on Facebook. There may be some good measures taken to prevent any sharing, but you can't protect what Facebook (or others) will do in the future. I already take issue with what happens (not from anything you've done, but proves my point) I log in to Amazon on my PC and search for items, I used Facebook on my PC and check a few posts. Then I go to Facebook on my phone and there are ads for things that I just searched for on Amazon in my Facebook feed. Facebook is my least trustworthy app I have. Your app may have mechanisms to prevent any further sharing of data in any kind, I just don't trust the big guys out there. They make their own rules and answer to no one.
I've got 325 apps that I use or have at least installed on my phone at one time or another and not one of them use a social media login other than that specific app, Facebook, etc. Decided I won't break that here, so just deleting the app.
I'll note for posterity too, I really have a bigger reason I'm not a fan of the common social media login. I share the house and pool with my partner. We don't share social media accounts, but we both test chemicals. The way this is implemented you then have to share one of the logins, not something I do, even though it is with someone I trust. We do have a shared email, hosted by a trusted email provider - Zoho, using our own domain. But only the big services are utilized.