Feat/um 305 unique session ch (#2065)

* Add session_data / session redis to CH.

* Add mysql migration.

tracker/index.js

@@ -173,7 +173,7 @@
     }
   };
 
-  const send = payload => {
+  const send = (payload, type = 'event') => {
     if (trackingDisabled()) return;
     const headers = {
       'Content-Type': 'application/json',
@@ -183,7 +183,7 @@
     }
     return fetch(endpoint, {
       method: 'POST',
-      body: JSON.stringify({ type: 'event', payload }),
+      body: JSON.stringify({ type, payload }),
       headers,
     })
       .then(res => res.text())
@@ -205,11 +205,14 @@
     return send(getPayload());
   };
 
+  const identify = data => send({ ...getPayload(), data }, 'identify');
+
   /* Start */
 
   if (!window.umami) {
     window.umami = {
       track,
+      identify,
     };
   }