PLT-1752/PLT-3567/PLT-3998 Highlighting links in search, unit tests for autolinking (#3865)

* Added highlighting to links when their URL includes the search term

* Decoupling UserStore from react-router to allow for unit tests involving it

* PLT-3998 Added SiteURL as an option to be passed into the text formatting code

* Removed reference to PreferenceStore and window from TextFormatting

* Refactored TextFormatting to remove remaining browser-only code

* Updated ChannelHeader and MessageWrapper to match the changes to TextFormatting

* Increased max listeners for Preference and Emoji stores

* PLT-3832 Added automated unit tests for autolinking

* PLT-3567 Rerender posts when mention keywords change

* Updated RHS and search to match the changes to TextFormatting

* Broke TextFormatting's dependency on the UserStore

webapp/utils/utils.jsx

@@ -1344,3 +1344,27 @@ export function isValidPassword(password) {
 export function getSiteURL() {
     return global.mm_config.SiteURL || window.location.origin;
 }
+
+export function handleFormattedTextClick(e) {
+    const mentionAttribute = e.target.getAttributeNode('data-mention');
+    const hashtagAttribute = e.target.getAttributeNode('data-hashtag');
+    const linkAttribute = e.target.getAttributeNode('data-link');
+
+    if (mentionAttribute) {
+        e.preventDefault();
+
+        searchForTerm(mentionAttribute.value);
+    } else if (hashtagAttribute) {
+        e.preventDefault();
+
+        searchForTerm(hashtagAttribute.value);
+    } else if (linkAttribute) {
+        const MIDDLE_MOUSE_BUTTON = 1;
+
+        if (!(e.button === MIDDLE_MOUSE_BUTTON || e.altKey || e.ctrlKey || e.metaKey || e.shiftKey)) {
+            e.preventDefault();
+
+            browserHistory.push(linkAttribute.value);
+        }
+    }
+}