Expected Behavior

To not store a string as string wrapped in a string. (extra double quotes). Unsure if there's some magic I haven't seen to prevent this.

https://github.com/actix/actix-extras/blob/master/actix-session/src/session.rs#L136-L147
We should check if the value is a string. If it's a string we should not use serde_json::to_string

Current Behavior

Using serde_json::to_string on everything including values of type string

Possible Solution

it seems there may have been uniformity reasons for not allowing types other than strings being stored, but I believe this makes the middleware less useful and more awkward.

Steps to Reproduce (for bugs)

1. using redis middleware insert a session value

Context

Double stringified strings result in all those values needing to be doubly unwrapped which is awkward. Would be nice to let users decide what kind of values they want to store and not wrap everything as string.

Your Environment

• Rust Version (I.e, output of rustc -V):
• Actix-* crate(s) Version:
  Latest stable.