Added VAPID Configuration Error type

Author: dimitribouniol

Sources/WebPush/Errors/VAPIDConfigurationError.swift

@@ -0,0 +1,30 @@
+//
+//  VAPIDConfigurationError.swift
+//  swift-webpush
+//
+//  Created by Dimitri Bouniol on 2024-12-13.
+//  Copyright © 2024 Mochi Development, Inc. All rights reserved.
+//
+
+import Foundation
+
+extension VAPID {
+    /// An error encountered during ``VAPID/Configuration`` initialization or decoding.
+    public struct ConfigurationError: LocalizedError, Hashable {
+        enum Kind {
+            case keysNotProvided
+        }
+        
+        var kind: Kind
+        
+        /// VAPID keys not found during initialization.
+        public static let keysNotProvided = Self(kind: .keysNotProvided)
+        
+        public var errorDescription: String? {
+            switch kind {
+            case .keysNotProvided:
+                "VAPID keys not found during initialization."
+            }
+        }
+    }
+}

Sources/WebPush/VAPID/VAPIDConfiguration.swift

@@ -46,14 +46,14 @@ extension VoluntaryApplicationServerIdentification {
             contactInformation: ContactInformation,
             expirationDuration: Duration = .hours(22),
             validityDuration: Duration = .hours(20)
-        ) throws {
+        ) throws(ConfigurationError) {
             self.primaryKey = primaryKey
             var keys = keys
             if let primaryKey {
                 keys.insert(primaryKey)
             }
             guard !keys.isEmpty
-            else { throw CancellationError() } // TODO: No keys error
+            else { throw .keysNotProvided }
 
             self.keys = keys
             var deprecatedKeys = deprecatedKeys ?? []
@@ -88,14 +88,14 @@ extension VoluntaryApplicationServerIdentification {
             primaryKey: Key?,
             keys: Set<Key>,
             deprecatedKeys: Set<Key>? = nil
-        ) throws {
+        ) throws(ConfigurationError) {
             self.primaryKey = primaryKey
             var keys = keys
             if let primaryKey {
                 keys.insert(primaryKey)
             }
             guard !keys.isEmpty
-            else { throw CancellationError() } // TODO: No keys error
+            else { throw .keysNotProvided }
 
             self.keys = keys
             var deprecatedKeys = deprecatedKeys ?? []