Add HTTPClientProtocol protocol

This provides a lightweight form of dependency injection for HTTP clients

Author: mattt

Sources/Basics/HTPClient+URLSession.swift

@@ -8,14 +8,14 @@ import struct TSCUtility.Versioning
 import FoundationNetworking
 #endif
 
-public struct URLSessionHTTPClient {
+public struct URLSessionHTTPClient: HTTPClientProtocol {
     private let configuration: URLSessionConfiguration
 
     public init(configuration: URLSessionConfiguration = .default) {
         self.configuration = configuration
     }
 
-    public func execute(request: HTTPClient.Request, callback: @escaping (Result<HTTPClient.Response, Error>) -> Void) {
+    public func execute(_ request: HTTPClient.Request, callback: @escaping (Result<HTTPClient.Response, Error>) -> Void) {
         let session = URLSession(configuration: self.configuration)
         let task = session.dataTask(with: request.urlRequest()) { data, response, error in
             if let error = error {

Sources/Basics/HTTPClient.swift

@@ -24,9 +24,13 @@ import Glibc
 import CRT
 #endif
 
+public protocol HTTPClientProtocol {
+    func execute(_ request: HTTPClientRequest, callback: @escaping (Result<HTTPClientResponse, Error>) -> Void)
+}
+
 // MARK: - HTTPClient
 
-public struct HTTPClient {
+public struct HTTPClient: HTTPClientProtocol {
     public typealias Configuration = HTTPClientConfiguration
     public typealias Request = HTTPClientRequest
     public typealias Response = HTTPClientResponse