Added countries app with get views (filter view and get by alpha2 view)

solution/pulse/countries/serializers.py

@@ -0,0 +1,9 @@
+from rest_framework import serializers
+
+from countries.models import Country
+
+
+class CountrySerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Country
+        fields = ["name", "alpha2", "alpha3", "region"]