Add registration and profile managment

[wolfeidau]

Just wondering if you were open to some additions around signup, registration and profile management.

Need it for a side project.

[RichardKnop]

@wolfeidau There is an empty package accounts in this repo meant to be filled with stuff like signup, permissions, profile management etc.

Currently not planning to include anything specific here as I would like to keep this project completely agnostic dealing with only oauth2. Different people manage accounts/profiles, permissions and so on differently.