Added a way to check the status of a subscriber's key against a configuration

Author: dimitribouniol

Sources/WebPush/VAPID/VAPIDConfiguration.swift

@@ -181,6 +181,24 @@ extension VAPID.Configuration {
         }
     }
 
+    /// The satus of a key as it relates to a configuration.
+    ///
+    /// - SeeAlso: ``WebPushManager/keyStatus(for:)``
+    public enum KeyStatus: Sendable, Hashable {
+        /// The key is valid and should continue to be used.
+        case valid
+        
+        /// The key had been deprecated.
+        ///
+        /// The user should be encouraged to re-register using a new key.
+        case deprecated
+        
+        /// The key is unknown to the configuration.
+        ///
+        /// The configuration should be investigated as all keys should be accounted for.
+        case unknown
+    }
+    
     public struct Duration: Hashable, Comparable, Codable, ExpressibleByIntegerLiteral, AdditiveArithmetic, Sendable {
         public let seconds: Int
 

Sources/WebPush/WebPushManager.swift

@@ -175,6 +175,18 @@ public actor WebPushManager: Sendable {
         vapidConfiguration.primaryKey?.id ?? vapidConfiguration.keys.randomElement()!.id
     }
 
+    /// Check the status of a key against the current configuration.
+    public nonisolated func keyStatus(for keyID: VAPID.Key.ID) -> VAPID.Configuration.KeyStatus {
+        guard let key = vapidKeyLookup[keyID]
+        else { return .unknown }
+        
+        if vapidConfiguration.deprecatedKeys?.contains(key) == true {
+            return .deprecated
+        }
+        
+        return .valid
+    }
+    
     /// Send a push message as raw data.
     ///
     /// The service worker you registered is expected to know how to decode the data you send.