Defining the user session

To define our user session, we must import the following:

// nanoservices/user-session-cache/cache-module/src/user_session.rs
use redis_module::{
    Context, RedisString, RedisError, RedisResult, RedisValue
};
use chrono::{DateTime, Utc, NaiveDateTime};

With this, our user session struct has the following definition:

// nanoservices/user-session-cache/cache-module/src/user_session.rs
pub struct UserSession {
    pub user_id: String,
    pub key: String,
    pub session_datetime: DateTime<Utc>,
}

Our user session then has the functions associated below:

// nanoservices/user-session-cache/cache-module/src/user_session.rs
impl UserSession {
    pub fn from_id(user_id: String)
    -> UserSession {
        . . .
    }
    pub fn check_timeout(&mut self, ctx: &Context)
    -> RedisResult {
        . . .
    }
    pub fn update_last_interacted(&self, ctx: &Context)
    -> RedisResult {
        . . .
    }
    pub fn get_counter(...