Replace App.HTTPClient calls after merge (#9387)

* Replace App.HTTPClient calls after merge

* Add missing import

app/opengraph.go

@@ -13,7 +13,7 @@ import (
 )
 
 func (a *App) GetOpenGraphMetadata(requestURL string) *opengraph.OpenGraph {
-	res, err := a.HTTPClient(false).Get(requestURL)
+	res, err := a.HTTPService.MakeClient(false).Get(requestURL)
 	if err != nil {
 		mlog.Error("GetOpenGraphMetadata request failed", mlog.String("requestURL", requestURL), mlog.Any("err", err))
 		return nil

app/post_metadata.go

@@ -225,7 +225,7 @@ func (a *App) getLinkMetadata(requestURL string, useCache bool) (*opengraph.Open
 
 	request.Header.Add("Accept", "text/html, image/*")
 
-	res, err := a.HTTPClient(false).Do(request) // TODO figure out a way to mock out the client for testing
+	res, err := a.HTTPService.MakeClient(false).Do(request)
 	if err != nil {
 		return nil, nil, err
 	}

app/post_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"sync/atomic"
 	"testing"
 	"time"