Cract cms can't connection Azure mysql

[hiake21c]

### Description

In Azure Mysql, username must include "@".
If it set Azure Msql in Craftcms, username will be cut off after "@".
And than, if it enter the database host (domain) of Azure Mysql, it converts to ip by Craftcms and tries to connect.
Azure SQL cannot be accessed by ip.
it must used domain name where connect to Azure data base.

Steps to reproduce

1. Make Azure mysql
2. set mysql to craftCMS

DB_SERVER='users_info.mysql.database.azure.com'
DB_USER='your_username@yours_username'

Additional info

• Craft version: 3.0
• PHP version: 7.0
• Database driver & version: mysql 5.6
• Plugins & versions:

I added my log

2020-07-22 21:32:33 [-][-][-][info][yii\db\Connection::open] Opening DB connection: mysql:host=test.mysql.database.azure.com;dbname=tera_craftcms_edge;port=3306
2020-07-22 21:32:33 [-][-][-][profile begin][yii\db\Connection::open] Opening DB connection: mysql:host=test.mysql.database.azure.com;dbname=tera_craftcms_edge;port=3306
2020-07-22 21:32:33 [-][-][-][profile end][yii\db\Connection::open] Opening DB connection: mysql:host=test.mysql.database.azure.com;dbname=tera_craftcms_edge;port=3306
2020-07-22 21:32:33 [-][-][-][error][craft\db\Connection::open] SQLSTATE[HY000] [1045] Access denied for user 'test_site_user'@'157.55.174.73' (using password: YES)
2020-07-22 21:32:33 [-][-][-][error][craft\db\Connection::open] SQLSTATE[HY000] [1045] Access denied for user 'test_site_user'@'157.55.174.73' (using password: YES)
2020-07-22 21:32:33 [-][-][-][error][craft\base\ApplicationTrait::getIsDbConnectionValid] There was a problem connecting to the database: Craft CMS can’t connect to the database with the credentials in config/db.php.
2020-07-22 21:32:33 [-][-][-][error][craft\errors\DbConnectException] PDOException: SQLSTATE[HY000] [1045] Access denied for user 'test_site_user'@'157.55.174.73' (using password: YES) in /var/shared/www/vendor/yiisoft/yii2/db/Connection.php:703
Stack trace:
#0 /var/shared/www/vendor/yiisoft/yii2/db/Connection.php(703): PDO->__construct()
#1 /var/shared/www/vendor/yiisoft/yii2/db/Connection.php(624): yii\db\Connection->createPdoInstance()
#2 /var/shared/www/vendor/craftcms/cms/src/db/Connection.php(150): yii\db\Connection->open()
#3 /var/shared/www/vendor/craftcms/cms/src/base/ApplicationTrait.php(799): craft\db\Connection->open()
#4 /var/shared/www/vendor/craftcms/cms/src/base/ApplicationTrait.php(281): craft\web\Application->getIsDbConnectionValid()
#5 /var/shared/www/vendor/craftcms/cms/src/services/Sites.php(1138): craft\web\Application->getIsInstalled()
#6 /var/shared/www/vendor/craftcms/cms/src/services/Sites.php(448): craft\services\Sites->_loadAllSites()
#7 /var/shared/www/vendor/yiisoft/yii2/base/Component.php(180): craft\services\Sites->setCurrentSite()
#8 /var/shared/www/vendor/yiisoft/yii2/BaseYii.php(558): yii\base\Component->__set()
#9 /var/shared/www/vendor/yiisoft/yii2/base/BaseObject.php(107): yii\BaseYii::configure()
#10 [internal function]: yii\base\BaseObject->__construct()
#11 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(400): ReflectionClass->newInstanceArgs()
#12 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(159): yii\di\Container->build()
#13 /var/shared/www/vendor/yiisoft/yii2/BaseYii.php(365): yii\di\Container->get()
#14 /var/shared/www/vendor/yiisoft/yii2/di/ServiceLocator.php(137): yii\BaseYii::createObject()
#15 /var/shared/www/vendor/yiisoft/yii2/base/Module.php(742): yii\di\ServiceLocator->get()
#16 /var/shared/www/vendor/craftcms/cms/src/web/Application.php(341): yii\base\Module->get()
#17 /var/shared/www/vendor/craftcms/cms/src/base/ApplicationTrait.php(1238): craft\web\Application->get()
#18 /var/shared/www/vendor/craftcms/cms/src/web/Request.php(185): craft\web\Application->getSites()
#19 /var/shared/www/vendor/yiisoft/yii2/base/BaseObject.php(109): craft\web\Request->init()
#20 [internal function]: yii\base\BaseObject->__construct()
#21 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(400): ReflectionClass->newInstanceArgs()
#22 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(159): yii\di\Container->build()
#23 /var/shared/www/vendor/yiisoft/yii2/BaseYii.php(365): yii\di\Container->get()
#24 /var/shared/www/vendor/craftcms/cms/src/config/app.web.php(13): yii\BaseYii::createObject()
#25 [internal function]: {closure}()
#26 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(524): call_user_func_array()
#27 /var/shared/www/vendor/yiisoft/yii2/BaseYii.php(349): yii\di\Container->invoke()
#28 /var/shared/www/vendor/yiisoft/yii2/di/ServiceLocator.php(137): yii\BaseYii::createObject()
#29 /var/shared/www/vendor/yiisoft/yii2/base/Module.php(742): yii\di\ServiceLocator->get()
#30 /var/shared/www/vendor/craftcms/cms/src/web/Application.php(341): yii\base\Module->get()
#31 /var/shared/www/vendor/yiisoft/yii2/web/Application.php(160): craft\web\Application->get()
#32 /var/shared/www/vendor/craftcms/cms/src/base/ApplicationTrait.php(1380): yii\web\Application->getRequest()
#33 /var/shared/www/vendor/craftcms/cms/src/web/Application.php(100): craft\web\Application->_preInit()
#34 /var/shared/www/vendor/yiisoft/yii2/base/BaseObject.php(109): craft\web\Application->init()
#35 /var/shared/www/vendor/yiisoft/yii2/base/Application.php(206): yii\base\BaseObject->__construct()
#36 /var/shared/www/vendor/craftcms/cms/src/web/Application.php(91): yii\base\Application->__construct()
#37 [internal function]: craft\web\Application->__construct()
#38 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(400): ReflectionClass->newInstanceArgs()
#39 /var/shared/www/vendor/yiisoft/yii2/di/Container.php(159): yii\di\Container->build()
#40 /var/shared/www/vendor/yiisoft/yii2/BaseYii.php(365): yii\di\Container->get()
#41 /var/shared/www/vendor/craftcms/cms/bootstrap/bootstrap.php(245): yii\BaseYii::createObject()
#42 /var/shared/www/vendor/craftcms/cms/bootstrap/web.php(51): require('/var/shared/www...')
#43 /var/shared/www/web/index.php(20): require('/var/shared/www...')
#44 {main}

[hiake21c]

I sovled this issue.

I can connect Azure mysql now after that I delete runtime directory.