MM-11855 Add App.HTTPService to allow mocking of HTTP client (#9359)

* MM-11855 Add App.HTTPService to allow mocking of HTTP client

* Initialize HTTPService earlier

app/http_service.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/mattermost/mattermost-server/utils"
+)
+
+// Wraps the functionality for creating a new http.Client to encapsulate that and allow it to be mocked when testing
+type HTTPService interface {
+	MakeClient(trustURLs bool) *http.Client
+	Close()
+}
+
+type HTTPServiceImpl struct {
+	app *App
+}
+
+func MakeHTTPService(app *App) HTTPService {
+	return &HTTPServiceImpl{app}
+}
+
+func (h *HTTPServiceImpl) MakeClient(trustURLs bool) *http.Client {
+	insecure := h.app.Config().ServiceSettings.EnableInsecureOutgoingConnections != nil && *h.app.Config().ServiceSettings.EnableInsecureOutgoingConnections
+
+	if trustURLs {
+		return utils.NewHTTPClient(insecure, nil, nil)
+	}
+
+	allowHost := func(host string) bool {
+		if h.app.Config().ServiceSettings.AllowedUntrustedInternalConnections == nil {
+			return false
+		}
+		for _, allowed := range strings.Fields(*h.app.Config().ServiceSettings.AllowedUntrustedInternalConnections) {
+			if host == allowed {
+				return true
+			}
+		}
+		return false
+	}
+
+	allowIP := func(ip net.IP) bool {
+		if !utils.IsReservedIP(ip) {
+			return true
+		}
+		if h.app.Config().ServiceSettings.AllowedUntrustedInternalConnections == nil {
+			return false
+		}
+		for _, allowed := range strings.Fields(*h.app.Config().ServiceSettings.AllowedUntrustedInternalConnections) {
+			if _, ipRange, err := net.ParseCIDR(allowed); err == nil && ipRange.Contains(ip) {
+				return true
+			}
+		}
+		return false
+	}
+
+	return utils.NewHTTPClient(insecure, allowHost, allowIP)
+}
+
+func (h *HTTPServiceImpl) Close() {
+	// Does nothing, but allows this to be overridden when mocking the service
+}