Add cnameTarget for apps using an external domain

We have 4 properties related to the domain:
1) location, is the subdomain location without information how to craft
a fqdn on the client
2) fqdn, the intended domain to reach the app
3) altDomain, just the value for the external domain, merely a db record
value
4) cnameTarget, mostly for display purpose on the client, which
otherwise has no way to build the original cloudron local fqdn

src/routes/apps.js

@@ -54,6 +54,7 @@ function removeInternalAppFields(app) {
         fqdn: app.fqdn,
         memoryLimit: app.memoryLimit,
         altDomain: app.altDomain,
+        cnameTarget: app.cnameTarget,
         xFrameOptions: app.xFrameOptions,
         sso: app.sso,
         debugMode: app.debugMode