Auto update expired TLS/SSL certificates

-Previously when manually linking TLS/SSL certificates from certbot, the certificates themselves would be automatically updated via certbot but the explorer was still referencing the old certificates in memory and would cause https connections to stop working once the certificates actually expired. The explorer now watches for changes to the certificate directory and will automatically refresh and use the new certificates without requiring any kind of restart.

app.js

@@ -877,18 +877,40 @@ app.use(function(err, req, res, next) {
 
 // determine if tls features should be enabled
 if (settings.webserver.tls.enabled == true) {
+  function readCertsSync() {
+    var tls_options = {};
+
+    try {
+      tls_options = {
+        key: db.fs.readFileSync(settings.webserver.tls.key_file),
+        cert: db.fs.readFileSync(settings.webserver.tls.cert_file),
+        ca: db.fs.readFileSync(settings.webserver.tls.chain_file)
+      };
+    } catch(e) {
+      console.warn('There was a problem reading tls certificates. Check that the certificate, chain and key paths are correct.');
+    }
+
+    return tls_options;
+  }
+
+  const https = require('https');
+  let httpd = https.createServer(readCertsSync(), app).listen(settings.webserver.tls.port);
+
   try {
-    var tls_options = {
-      key: db.fs.readFileSync(settings.webserver.tls.key_file),
-      cert: db.fs.readFileSync(settings.webserver.tls.cert_file),
-      ca: db.fs.readFileSync(settings.webserver.tls.chain_file)
-    };
+    let waitForCertsToRefresh;
+
+    // watch for changes to the certificate directory
+    db.fs.watch(path.dirname(settings.webserver.tls.key_file), () => {
+      clearTimeout(waitForCertsToRefresh);
+
+      // refresh certificates as they are changed on disk
+      waitForCertsToRefresh = setTimeout(() => {
+        httpd.setSecureContext(readCertsSync());
+      }, 1000);
+    });
   } catch(e) {
     console.warn('There was a problem reading tls certificates. Check that the certificate, chain and key paths are correct.');
   }
-
-  var https = require('https');
-  https.createServer(tls_options, app).listen(settings.webserver.tls.port);
 }
 
 // get the latest git commit id (if exists)