feat: Add Default implementation for Harmony Id along with documentation.

This Id implementation is optimized for ease of use. Ids are prefixed with the unix epoch and suffixed with 7 alphanumeric characters. But Ids can also contain any String the user wants to pass it

harmony/Cargo.toml

@@ -6,6 +6,8 @@ readme.workspace = true
 license.workspace = true
 
 [dependencies]
+rand = "0.9"
+hex = "0.4"
 libredfish = "0.1.1"
 reqwest = { version = "0.11", features = ["blocking", "json"] }
 russh = "0.45.0"

harmony/src/domain/data/id.rs

@@ -1,5 +1,23 @@
+use std::time::SystemTime;
+use std::time::UNIX_EPOCH;
+use rand::distr::Alphanumeric;
+use rand::distr::SampleString;
+
 use serde::{Deserialize, Serialize};
 
+/// A unique identifier designed for ease of use.
+///
+/// You can pass it any String to use and Id, or you can use the default format with `Id::default()`
+///
+/// The default format looks like this
+///
+/// `462d4c_g2COgai`
+///
+/// The first part is the unix timesamp in hexadecimal which makes Id easily sorted by creation time.
+/// Second part is a serie of 7 random characters.
+///
+/// **It is not meant to be very secure or unique**, it is suitable to generate up to 10 000 items per
+/// second with a reasonable collision rate of 0,000014 % as calculated by this calculator : https://kevingal.com/apps/collision.html
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct Id {
     value: String,
@@ -19,6 +37,17 @@ impl std::fmt::Display for Id {
 
 impl Default for Id {
     fn default() -> Self {
-        todo!()
+        let start = SystemTime::now();
+        let since_the_epoch = start
+            .duration_since(UNIX_EPOCH)
+            .expect("Time went backwards");
+        let timestamp = since_the_epoch.as_secs();
+
+        let hex_timestamp = format!("{:x}", timestamp & 0xffffff);
+
+        let random_part: String = Alphanumeric.sample_string(&mut rand::rng(), 7);
+
+        let value = format!("{}_{}", hex_timestamp, random_part);
+        Self { value }
     }
 }