MM-10603: Ignore Redirects and Other Changes when Displaying Link Previews (#9025)

* Don't use redirected URL in link preview.

* Only show preview if OG data is provided.

app/post.go

@@ -765,6 +765,11 @@ func (a *App) GetOpenGraphMetadata(requestURL string) *opengraph.OpenGraph {
 
 	makeOpenGraphURLsAbsolute(og, requestURL)
 
+	// The URL should be the link the user provided in their message, not a redirected one.
+	if og.URL != "" {
+		og.URL = requestURL
+	}
+
 	return og
 }