This is excellent, especially the diagrams. I'd love to see a explanation of the security implications of each flow. As I understand it the "most secure" flow

This is excellent, especially the diagrams. I'd love to see a explanation of the security implications of each flow. As I understand it the "most secure" flow is OAuth 1.0a (three-legged), but its a total pain so it is mostly avoided. OAuth 2.0 is dramatically simpler, but there are bespoke additions (Google and Facebook come to mind) that you have to handle, typically in the name of security. I am ignorant of all the implications and would like a guide.