Started aligning app-wide outbound http calling behaviour

app/Http/HttpRequestService.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace BookStack\Http;
+
+use GuzzleHttp\Client;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Middleware;
+use GuzzleHttp\Psr7\Request as GuzzleRequest;
+use Psr\Http\Client\ClientInterface;
+
+class HttpRequestService
+{
+    protected ?HandlerStack $handler = null;
+
+    /**
+     * Build a new http client for sending requests on.
+     */
+    public function buildClient(int $timeout, array $options): ClientInterface
+    {
+        $defaultOptions = [
+            'timeout' => $timeout,
+            'handler' => $this->handler,
+        ];
+
+        return new Client(array_merge($options, $defaultOptions));
+    }
+
+    /**
+     * Create a new JSON http request for use with a client.
+     */
+    public function jsonRequest(string $method, string $uri, array $data): GuzzleRequest
+    {
+        $headers = ['Content-Type' => 'application/json'];
+        return new GuzzleRequest($method, $uri, $headers, json_encode($data));
+    }
+
+    /**
+     * Mock any http clients built from this service, and response with the given responses.
+     * Returns history which can then be queried.
+     * @link https://docs.guzzlephp.org/en/stable/testing.html#history-middleware
+     */
+    public function mockClient(array $responses = []): HttpClientHistory
+    {
+        $container = [];
+        $history = Middleware::history($container);
+        $mock = new MockHandler($responses);
+        $this->handler = HandlerStack::create($mock);
+        $this->handler->push($history, 'history');
+
+        return new HttpClientHistory($container);
+    }
+
+    /**
+     * Clear mocking that has been set up for clients.
+     */
+    public function clearMocking(): void
+    {
+        $this->handler = null;
+    }
+}