Added current and previous version information.

Closes #614.

src/app/utils/logger.ts

@@ -1,5 +1,33 @@
 import { environment } from 'environments/environment';
 
+const PREVIOUS_VERSION_KEY = 'altair__debug_previous_version';
+const CURRENT_VERSION_KEY = 'altair__debug_current_version';
+const previousVersion = () => localStorage.getItem(PREVIOUS_VERSION_KEY);
+const currentVersion = () => localStorage.getItem(CURRENT_VERSION_KEY);
+
+if (currentVersion() !== environment.version) {
+  // New app version
+  // prev = current
+  // current = env.version
+  localStorage.setItem(PREVIOUS_VERSION_KEY, currentVersion());
+  localStorage.setItem(CURRENT_VERSION_KEY, environment.version);
+}
+
+Object.defineProperty(window, '__ENABLE_DEBUG_MODE__', {
+  get() {
+    return window['_ALTAIR__ENABLE_DEBUG_MODE__'];
+  },
+  set(value) {
+    if (value) {
+      // Display debug information.
+      console.group('⚙️🛠Altair Debug Information');
+      console.log('Previous version:', previousVersion());
+      console.log('Current version:', currentVersion());
+      console.groupEnd();
+    }
+    window['_ALTAIR__ENABLE_DEBUG_MODE__'] = value;
+  }
+});
 
 /**
  * Only logs in development or when __ENABLE_DEBUG_MODE__ flag is true