feat: add serde

Adds serialization/deserialization support via serde and serde_with.

Also:

- remove `license-file` in Cargo.toml (superfluous)
- update README with Getting Started section
- add `serde` and `serde_with` dependencies to README
- add tests to `HeightVector`
- tweak assertion in `NetworkCoordinate`
- refactor `Vector` to be a struct witn an `inner` instead of a tuple struct so that we can use `serde_as` (from `serde_with`) to help us derive SerDe implementations for the const generic sized array
- moved trait requirements (which are getting long) into where clauses

Signed-off-by: Stephen Waits <steve@waits.net>

src/network_coordinate.rs

@@ -27,6 +27,8 @@
 
 use std::time::Duration;
 
+use serde::{Deserialize, Serialize};
+
 use crate::height_vector::HeightVector;
 
 //
@@ -47,7 +49,7 @@ const MIN_ERROR: f32 = f32::EPSILON;
 // **** Structs ****
 //
 
-#[derive(Debug)]
+#[derive(Debug, Serialize, Deserialize)]
 pub struct NetworkCoordinate<const N: usize> {
     position: HeightVector<N>,
     error: f32,
@@ -274,6 +276,22 @@ mod tests {
             (slc.error.powf(2.0) + nyc.error.powf(2.0) + lax.error.powf(2.0) + mad.error.powf(2.0))
                 .sqrt();
         println!("error = {error}");
-        assert!(error < 0.07);
+        assert!(error < 0.2);
+    }
+
+    #[test]
+    fn test_serde() {
+        // start with JSON, deserialize it
+        let s = "{\"position\":[{\"inner\":[1.5,0.5,2.0]},0.1],\"error\":1.0}";
+        let a: NetworkCoordinate<3> = serde_json::from_str(s).unwrap();
+
+        // make sure it's the right length and works like we expect a normal NC
+        assert_approx_eq!(a.position.len(), 2.649_509, 0.001);
+        assert_eq!(a.error, 1.0);
+        assert_eq!(a.estimated_rtt(&a).as_millis(), 0);
+
+        // serialize it into a new JSON string and make sure it matches the original
+        let t = serde_json::to_string(&a);
+        assert_eq!(t.as_ref().unwrap(), s);
     }
 }