feat(binding_coap): add tryParse method to CoapSubprotocol

Author: JKRhb

lib/src/binding_coap/coap_definitions.dart

@@ -55,4 +55,15 @@ enum CoapRequestMethod {
 enum CoapSubprotocol {
   /// Subprotocol for observing CoAP resources.
   observe,
+  ;
+
+  /// Tries to match the given [subprotocol] string to one of the known
+  /// [CoapSubprotocol.values].
+  static CoapSubprotocol? tryParse(String subprotocol) {
+    if (subprotocol == "cov:observe") {
+      return CoapSubprotocol.observe;
+    }
+
+    return null;
+  }
 }