Replace ring by rust-argon2, rand, hmac and sha2

[thespooler]

Feature

As discussed in issue #55 and #71, it seems that moving away from ring is the most sensible way to integrate with other projects that might have conflicting package version requirements.

Alternatives

Leave ring, split crates, try to follow other projects dependencies and match ring versions accordingly.

Context

actix-web 2.0 when used with actix-identity or actix-session requires ring 0.16.9, while oxide-auth requires ring < 0.15.

Tracking pull request

• Replace pbkdf2 by Argon2 in registrar Replace pbkdf2 with argon2 via rust-argon2 #86
• Replace ring in generator Remove ring from pkce and generator #85
• Replace ring in registrar Replace pbkdf2 with argon2 via rust-argon2 #86
• Replace ring in pkce code_grant extension Remove ring from pkce and generator #85
• Remove ring from dependencies and tests Remove ring #87

Related

• Update to actix-web 2.0 Update to actix-web 2.0 #71
• Ring question Ring question #55
• Ring 0.16 actix web 2.0 Ring 0.16 actix web 2.0 #73