add server side tracking to docs (#2556)

docs/_static/js/serversidetracking.js

@@ -0,0 +1,54 @@
+function getRandomString(length=25) {
+    var result           = '';
+    var characters       = 'abcdefghijklmnopqrstuvwxyz0123456789';
+    var charactersLength = characters.length;
+    for ( var i = 0; i < length; i++ ) {
+      result += characters.charAt(Math.floor(Math.random() * charactersLength));
+   }
+   return result;
+}
+function getEventId() {
+    return Math.floor(new Date().getTime() / 1000) + '-' + getRandomString(25);
+}
+
+
+function setCookies(cname, cvalue, exdays) {
+  const d = new Date();
+  d.setTime(d.getTime() + (exdays*24*60*60*1000));
+  let expires = "expires="+ d.toUTCString();
+  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
+}
+function getCookie(cname) {
+  let name = cname + "=";
+  let decodedCookie = decodeURIComponent(document.cookie);
+  let ca = decodedCookie.split(';');
+  for(let i = 0; i <ca.length; i++) {
+    let c = ca[i];
+    while (c.charAt(0) == ' ') {
+      c = c.substring(1);
+    }
+    if (c.indexOf(name) == 0) {
+      return c.substring(name.length, c.length);
+    }
+  }
+  return "";
+}
+
+if( getCookie('userId').length < 1 ) {
+    setCookies('userId',getEventId(),365);
+}
+
+// Google Tag Manager
+if( typeof dataLayer === 'undefined' ) {
+    let eventId =  getEventId();
+    dataLayer = [{'eventId': eventId}];
+    $.post( "https://specflow.org/wp-content/plugins/fb-sst/t.php", {
+        'eventId':      eventId,
+        'sourceUrl':    window.location.origin + window.location.pathname,
+        'event_name':   'PageView',
+        'external_id':  getCookie('userId'),
+        'fbc':          getCookie('_fbc'),
+        'fbp':          getCookie('_fbp'),
+        'analytics_storage':getCookie('v_c_analytics_storage'),
+    } );
+} 

docs/conf.py

@@ -63,6 +63,7 @@
 
 html_js_files = [
     'js/hotjar.js',
+    'js/serversidetracking.js'
 ]
 
 html_baseurl = 'https://docs.specflow.org/projects/specflow/'