Refactor dependencies to reduce code base size (#111)

Use crates to reduce code base size :

* `actix-remote-ip` to safely determine user IP location
* `light-openid` for the OpenID primitives & as client to handle federation

Reviewed-on: #111

src/utils/mod.rs

@@ -1,5 +1,4 @@
 pub mod crypt_utils;
 pub mod err;
-pub mod network_utils;
 pub mod string_utils;
 pub mod time;