well basically OAuth2 Resource Owner Password Credentials Grant (https://tools.ietf.org/html/rfc6749#section-4.3 https://tools.ietf.org/html/rfc6749#section-4.3

well basically OAuth2 Resource Owner Password Credentials Grant (https://tools.ietf.org/html/rfc6749#section-4.3 https://tools.ietf.org/html/rfc6749#section-4.3) Is basically the same thing than Login Form + Cookie, just that you return the Token instead of setting a Cookie. So it's only more complex if you also act as a OAuth Provider, that implements all the other Flows.