Add db migration scripts

This adds domains table and adjusts the apps and mailboxes table accordingly

Also ensure we explicitly set the table collation, this is required
for the foreign key from apps table (utf8) and the newly created
domains table, which by default now would be utf8mb4

Put db table constraint for mailboxes.domain

Update the schema file

src/platform.js

@@ -12,10 +12,8 @@ var apps = require('./apps.js'),
     async = require('async'),
     config = require('./config.js'),
     certificates = require('./certificates.js'),
-    DatabaseError = require('./databaseerror.js'),
     debug = require('debug')('box:platform'),
     domains = require('./domains.js'),
-    DomainError = domains.DomainError,
     fs = require('fs'),
     hat = require('hat'),
     infra = require('./infra_version.js'),
@@ -25,7 +23,6 @@ var apps = require('./apps.js'),
     safe = require('safetydance'),
     semver = require('semver'),
     settings = require('./settings.js'),
-    settingsdb = require('./settingsdb.js'),
     shell = require('./shell.js'),
     taskmanager = require('./taskmanager.js'),
     user = require('./user.js'),
@@ -67,7 +64,6 @@ function start(callback) {
     debug('Updating infrastructure from %s to %s', existingInfra.version, infra.version);
 
     async.series([
-        migrateDNSSettings,
         stopContainers.bind(null, existingInfra),
         startAddons.bind(null, existingInfra),
         removeOldImages,
@@ -381,24 +377,3 @@ function startApps(existingInfra, callback) {
         apps.configureInstalledApps(callback);
     }
 }
-
-// This is only used when updating from single to multi domain support
-// REMOVE later!
-function migrateDNSSettings(callback) {
-    assert.strictEqual(typeof callback, 'function');
-
-    settingsdb.get('dns_config', function (error, result) {
-        if (error && error.reason !== DatabaseError.NOT_FOUND) return callback(error);
-
-        const dnsConfig = result ? safe.JSON.parse(result) : { provider: 'manual' };
-
-        domains.get(config.fqdn(), function (error, result) {
-            if (error && error.reason !== DomainError.NOT_FOUND) return callback(error);
-
-            // if domain is already in the table, nothing to do
-            if (result) return callback(null);
-
-            domains.add(config.fqdn(), config.zoneName(), dnsConfig, callback);
-        });
-    });
-}