dev: start parser refactor on the main codebase, see #65 and #44

Things were getting a bit complicated and slow with the old parser so I decided to continue #44's work on the main codebase.

lib/parser/contents/classes/AnalyticsMainAppKeyMetrics.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const DataModelSection = require('./DataModelSection');
+
+class AnalyticsMainAppKeyMetrics {
+  type = 'analyticsMainAppKeyMetricsModel';
+  
+  constructor(data) {
+    this.period = data.cardData.periodLabel;
+  
+    const metrics_data = data.cardData.sections[0].analyticsKeyMetricsData;
+  
+    this.sections = metrics_data.dataModel.sections.map((section) => new DataModelSection(section));
+  }
+}
+
+module.exports = AnalyticsMainAppKeyMetrics;