feat: Add Fields impl for Link

crates/types/src/link.rs

@@ -1,6 +1,6 @@
 //! Links.
 
-use crate::{mime::APPLICATION_GEOJSON, Error, Href, Result, SelfHref};
+use crate::{mime::APPLICATION_GEOJSON, Error, Fields, Href, Result, SelfHref};
 use mime::APPLICATION_JSON;
 use serde::{Deserialize, Serialize};
 use serde_json::{Map, Value};
@@ -688,6 +688,16 @@ impl Link {
     }
 }
 
+impl Fields for Link {
+    fn fields(&self) -> &Map<String, Value> {
+        &self.additional_fields
+    }
+
+    fn fields_mut(&mut self) -> &mut Map<String, Value> {
+        &mut self.additional_fields
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::Link;
@@ -701,6 +711,25 @@ mod tests {
         assert!(link.title.is_none());
     }
 
+    mod fields {
+        use serde_json::Value;
+        use stac::{Fields, Link};
+
+        #[test]
+        fn empty() {
+            let link = Link::new("an-href", "a-rel");
+            assert!(link.fields().is_empty());
+        }
+
+        #[test]
+        fn set_get() {
+            let mut link = Link::new("an-href", "a-rel");
+            _ = link.set_field("some", "value");
+            assert!(link.field("some") == Some(&Value::from("value")));
+            assert!(*link.fields() == link.additional_fields);
+        }
+    }
+
     #[test]
     fn skip_serializing() {
         let link = Link::new("an-href", "a-rel");