Add Sendable conformance

Author: colemancda

Sources/XMLCoder/Auxiliaries/Attribute.swift

@@ -40,6 +40,7 @@ extension Attribute: Codable where Value: Codable {
 
 extension Attribute: Equatable where Value: Equatable {}
 extension Attribute: Hashable where Value: Hashable {}
+extension Attribute: Sendable where Value: Sendable {}
 
 extension Attribute: ExpressibleByIntegerLiteral where Value: ExpressibleByIntegerLiteral {
     public typealias IntegerLiteralType = Value.IntegerLiteralType

Sources/XMLCoder/Auxiliaries/Element.swift

@@ -40,3 +40,4 @@ extension Element: Codable where Value: Codable {
 
 extension Element: Equatable where Value: Equatable {}
 extension Element: Hashable where Value: Hashable {}
+extension Element: Sendable where Value: Sendable {}

Sources/XMLCoder/Auxiliaries/ElementAndAttribute.swift

@@ -41,3 +41,4 @@ extension ElementAndAttribute: Codable where Value: Codable {
 
 extension ElementAndAttribute: Equatable where Value: Equatable {}
 extension ElementAndAttribute: Hashable where Value: Hashable {}
+extension ElementAndAttribute: Sendable where Value: Sendable {}

Sources/XMLCoder/Auxiliaries/XMLCoderElement.swift

@@ -8,8 +8,8 @@
 
 import Foundation
 
-struct XMLCoderElement: Equatable {
-    struct Attribute: Equatable {
+struct XMLCoderElement: Equatable, Sendable {
+    struct Attribute: Equatable, Sendable {
         let key: String
         let value: String
     }

Sources/XMLCoder/Auxiliaries/XMLHeader.swift

@@ -11,7 +11,7 @@ import Foundation
 /// Type that allows overriding XML header during encoding. Pass a value of this type to the `encode`
 /// function of `XMLEncoder` to specify the exact value of the header you'd like to see in the encoded
 /// data.
-public struct XMLHeader {
+public struct XMLHeader: Sendable {
     /// The XML standard that the produced document conforms to.
     public let version: Double?
 

Sources/XMLCoder/Auxiliaries/XMLKey.swift

@@ -9,7 +9,7 @@
 import Foundation
 
 /// Shared Key Types
-struct XMLKey: CodingKey {
+struct XMLKey: CodingKey, Sendable {
     public let stringValue: String
     public let intValue: Int?