Extracted members csv serialization logic into separate module

no issue

- This is prep work for extraction into members repository.

ghost/members-csv/unparse

@@ -0,0 +1,33 @@
+const _ = require('lodash');
+const papaparse = require('papaparse');
+
+const unparse = (members) => {
+    const mappedMembers = members.map((member) => {
+        let stripeCustomerId;
+
+        if (member.stripe) {
+            stripeCustomerId = _.get(member, 'stripe.subscriptions[0].customer.id');
+        }
+        let labels = [];
+        if (member.labels) {
+            labels = `${member.labels.map(l => l.name).join(',')}`;
+        }
+
+        return {
+            id: member.id,
+            email: member.email,
+            name: member.name,
+            note: member.note,
+            subscribed_to_emails: member.subscribed,
+            complimentary_plan: member.comped,
+            stripe_customer_id: stripeCustomerId,
+            created_at: member.created_at,
+            deleted_at: member.deleted_at,
+            labels: labels
+        };
+    });
+
+    return papaparse.unparse(mappedMembers);
+};
+
+module.exports.unparse = unparse;