Add order-by logic to database queries

[xelab04]

Refer to #490

[xelab04]

https://docs.rs/sea-query/latest/sea_query/query/trait.OrderedStatement.html
The sea query docs make a reference to order_by_expr which takes expr: SimpleExpr, order: Order

I'm not exactly sure how to plug sea query into this?

[xelab04]

Right, updated it to use seaquery's own order_by method. I'm not getting the types down for the time being, will work on it more later.

[xelab04]

I have changed it so that instead of ordering on a string of the field name, it uses the fieldref identifier.
So, it would look something like this:

use cot::db::model;
use cot::db::query::Query;
use sea_query::Order; (?)

#[model]
struct User {
    #[model(primary_key)]
    id: i32,
    age: i32,
}

let query = Query::<User>::new().order_by(User::age, Order::Asc);

Last bit is the ownership because it's not happy with the .clone()
And of course, tests