internal-links: Open file attachments within the app.

Changing the behaviour of opening the attachments in the
default browser to the app. This commit enables users to
download the attachments. If the attachment type is image
then we open the same in the app though users need to
click on the go-back button.

To-do - Open the image link in a lightbox.

Improves: #469.

Author: akashnimare

app/renderer/js/components/webview.js

@@ -49,7 +49,13 @@ class WebView extends BaseComponent {
 			const { url } = event;
 			const domainPrefix = DomainUtil.getDomain(this.props.index).url;
 
-			if (LinkUtil.isInternal(domainPrefix, url) || url === (domainPrefix + '/')) {
+			// Whitelist URLs which are allowed to be opened in the app
+			const isWhiteListURL =
+				LinkUtil.isInternal(domainPrefix, url) ||
+				url === domainPrefix + '/' ||
+				url.includes(domainPrefix + '/user_uploads/'); // URL containing the file attachments
+
+			if (isWhiteListURL) {
 				event.preventDefault();
 				this.$el.loadURL(url);
 			} else {