Conform StripeClient to Sendable

Use Swift 5.10 as minimum version

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.7
+// swift-tools-version:5.10
 import PackageDescription
 
 let package = Package(
@@ -13,7 +13,7 @@ let package = Package(
         .library(name: "StripeKit", targets: ["StripeKit"])
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-server/async-http-client.git", from: "1.1.0"),
+        .package(url: "https://github.com/swift-server/async-http-client.git", from: "1.24.0"),
         .package(url: "https://github.com/apple/swift-crypto.git", "1.0.0" ..< "4.0.0"),
     ],
     targets: [

Sources/StripeKit/Checkout/SessionRoutes.swift

@@ -9,7 +9,7 @@ import NIO
 import NIOHTTP1
 import Foundation
 
-public protocol SessionRoutes {
+public protocol SessionRoutes: Sendable {
     /// Creates a Session object.
     /// - Parameters:
     ///   - lineItems: A list of items the customer is purchasing. Use this parameter to pass one-time or recurring Prices. For payment mode, there is a maximum of 100 line items, however it is recommended to consolidate line items if there are more than a few dozen. For subscription mode, there is a maximum of 20 line items with recurring Prices and 20 line items with one-time Prices. Line items with one-time Prices will be on the initial invoice only.

Sources/StripeKit/StripeAPIRoute.swift

@@ -8,7 +8,7 @@
 import Foundation
 import NIOHTTP1
 
-public protocol StripeAPIRoute {
+public protocol StripeAPIRoute: Sendable {
     var headers: HTTPHeaders { get set }
 
     /// Headers to send with the request.

Sources/StripeKit/StripeClient.swift

@@ -8,7 +8,7 @@
 import NIO
 import AsyncHTTPClient
 
-public final class StripeClient {
+public struct StripeClient: Sendable {
     // MARK: - CORE RESOURCES
     public var balances: BalanceRoutes
     public var balanceTransactions: BalanceTransactionRoutes

Tests/StripeKitTests/ExpandableTests.swift

@@ -1,7 +1,7 @@
 import XCTest
 @testable import StripeKit
 
-class ExpandableTests: XCTestCase {
+final class ExpandableTests: XCTestCase {
 
     func testDynamicExpandable_decodesProperly() throws {
 

Tests/StripeKitTests/QueryEncodingTests.swift

@@ -1,7 +1,7 @@
 import XCTest
 @testable import StripeKit
 
-class QueryEncodingTests: XCTestCase {
+final class QueryEncodingTests: XCTestCase {
 
     func testSimpleQueryEncodedProperly() throws {
         let query = [

Tests/StripeKitTests/SignatureVerificationTests.swift

@@ -2,7 +2,7 @@ import XCTest
 @testable import StripeKit
 import Crypto
 
-class SignatureVerificationTests: XCTestCase {
+final class SignatureVerificationTests: XCTestCase {
     var jsonData: Data = try! JSONEncoder().encode(["key": "value"])
     var secret: String = "SECRET"