Add DNS wildcard backend

It assumes that the user setup the wildcard DNS entry manually.

src/dns/wildcard.js

@@ -0,0 +1,62 @@
+'use strict';
+
+exports = module.exports = {
+    upsert: upsert,
+    get: get,
+    del: del,
+    getChangeStatus: getChangeStatus
+};
+
+var assert = require('assert'),
+    debug = require('debug')('box:dns/wildcard'),
+    SubdomainError = require('../subdomains.js').SubdomainError,
+    sysinfo = require('..sysinfo.js'),
+    util = require('util');
+
+function upsert(dnsConfig, zoneName, subdomain, type, values, callback) {
+    assert.strictEqual(typeof dnsConfig, 'object');
+    assert.strictEqual(typeof zoneName, 'string');
+    assert.strictEqual(typeof subdomain, 'string');
+    assert.strictEqual(typeof type, 'string');
+    assert(util.isArray(values));
+    assert.strictEqual(typeof callback, 'function');
+
+    debug('upsert: %s for zone %s of type %s with values %j', subdomain, zoneName, type, values);
+
+    return callback();
+}
+
+function get(dnsConfig, zoneName, subdomain, type, callback) {
+    assert.strictEqual(typeof dnsConfig, 'object');
+    assert.strictEqual(typeof zoneName, 'string');
+    assert.strictEqual(typeof subdomain, 'string');
+    assert.strictEqual(typeof type, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    if (type !== 'A') return callback(null, [ ]);
+
+    sysinfo.getIp(function (error, ip) {
+        if (error) return callback(new SubdomainError(SubdomainError.INTERNAL_ERROR, error.message));
+
+        return callback(null, [ ip ]);
+    });
+}
+
+function del(dnsConfig, zoneName, subdomain, type, values, callback) {
+    assert.strictEqual(typeof dnsConfig, 'object');
+    assert.strictEqual(typeof zoneName, 'string');
+    assert.strictEqual(typeof subdomain, 'string');
+    assert.strictEqual(typeof type, 'string');
+    assert(util.isArray(values));
+    assert.strictEqual(typeof callback, 'function');
+
+    return callback();
+}
+
+function getChangeStatus(dnsConfig, changeId, callback) {
+    assert.strictEqual(typeof dnsConfig, 'object');
+    assert.strictEqual(typeof changeId, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    callback(null, 'INSYNC');
+}