More or less all the functionality for selectable unsubscription process. Not tested yet!

Sending emails moved completely to controller. It felt strange to have some emails sent from the controller and some of them from the model.
Confirmations refactored to an independent model that can be potentially used also for other actions that need an email confirmation.

lib/models/confirmations.js

@@ -0,0 +1,90 @@
+'use strict';
+
+let db = require('../db');
+let shortid = require('shortid');
+let helpers = require('../helpers');
+
+/*
+    Adds new entry to the confirmations tables. Generates confirmation cid, which it returns.
+ */
+module.exports.addConfirmation = (listId, action, ip, data, callback) => {
+    let cid = shortid.generate();
+
+    db.getConnection((err, connection) => {
+        if (err) {
+            return callback(err);
+        }
+
+        let query = 'INSERT INTO confirmations (cid, list, action, ip, data) VALUES (?,?,?,?,?)';
+        connection.query(query, [cid, list, action, ip, JSON.stringify(data || {})], (err, result) => {
+            connection.release();
+            if (err) {
+                return callback(err);
+            }
+
+            if (!result || !result.affectedRows) {
+                return callback(null, false);
+            }
+
+            return callback(null, cid);
+        });
+    });
+};
+
+/*
+    Atomically retrieves confirmation from the database, removes it from the database and returns it.
+ */
+module.exports.takeConfirmation = (cid, callback) => {
+    db.getConnection((err, connection) => {
+        if (err) {
+            return callback(err);
+        }
+
+        connection.beginTransaction(err => {
+            if (err) {
+                connection.release();
+                return callback(err);
+            }
+
+            let query = 'SELECT cid, list, action, ip, data FROM confirmations WHERE cid=? LIMIT 1';
+            connection.query(query, [cid], (err, rows) => {
+                if (err) {
+                    return helpers.rollbackAndReleaseConnection(connection, () => callback(err));
+                }
+
+                if (!rows || !rows.length) {
+                    return helpers.rollbackAndReleaseConnection(connection, () => callback(null, false));
+                }
+
+                connection.query('DELETE FROM confirmations WHERE `cid`=? LIMIT 1', [cid], () => {
+                    if (err) {
+                        return helpers.rollbackAndReleaseConnection(connection, () => callback(err));
+                    }
+
+                    connection.commit(err => {
+                        if (err) {
+                            return helpers.rollbackAndReleaseConnection(connection, () => callback(err));
+                        }
+                        connection.release();
+
+                        let data;
+                        try {
+                            data = JSON.parse(rows[0].data);
+                        } catch (E) {
+                            data = {};
+                        }
+
+                        const result = {
+                            listId: rows[0].list,
+                            action: rows[0].action,
+                            ip: rows[0].ip,
+                            data
+                        };
+
+                        return callback(null, result);
+                    });
+                });
+            });
+        });
+    });
+};