feat(@angular/cli): ping back when user opts out of analytics

On prompt only, does not contain any user info. Since prompt should be only
shown at install or first run, this is not going to ping more than once and
the users privacy is also protected.

Author: hansl

packages/angular/cli/models/analytics.ts

@@ -410,6 +410,11 @@ export async function promptGlobalAnalytics(force = false) {
             ${colors.yellow('ng analytics off')}
       `);
       console.log('');
+    } else {
+      // Send back a ping with the user `optout`. This is the only thing we send.
+      const ua = new UniversalAnalytics(AnalyticsProperties.AngularCliDefault, 'optout');
+      ua.pageview('/telemetry/optout');
+      await ua.flush();
     }
 
     return true;
@@ -459,6 +464,11 @@ export async function promptProjectAnalytics(force = false): Promise<boolean> {
             ${colors.yellow('ng analytics project off')}
       `);
       console.log('');
+    } else {
+      // Send back a ping with the user `optout`. This is the only thing we send.
+      const ua = new UniversalAnalytics(AnalyticsProperties.AngularCliDefault, 'optout');
+      ua.pageview('/telemetry/project/optout');
+      await ua.flush();
     }
 
     return true;