Handle ER_DBACCESS_DENIED_ERROR code in mysql2 adapter

During the process of adding adapter tests to test the different types of connection errors,
the ER_DBACCESS_DENIED_ERROR code was discovered to be not handled. It is the same as
ER_ACCESS_DENIED_ERROR except that a database has been given.

https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html#error_er_dbaccess_denied_error

Co-authored-by: Adrianna Chang <[email protected]>

Author: jenshenny

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -21,10 +21,11 @@ def mysql2_connection(config)
   module ConnectionAdapters
     # = Active Record MySQL2 Adapter
     class Mysql2Adapter < AbstractMysqlAdapter
-      ER_BAD_DB_ERROR        = 1049
-      ER_ACCESS_DENIED_ERROR = 1045
-      ER_CONN_HOST_ERROR     = 2003
-      ER_UNKNOWN_HOST_ERROR  = 2005
+      ER_BAD_DB_ERROR           = 1049
+      ER_DBACCESS_DENIED_ERROR  = 1044
+      ER_ACCESS_DENIED_ERROR    = 1045
+      ER_CONN_HOST_ERROR        = 2003
+      ER_UNKNOWN_HOST_ERROR     = 2005
 
       ADAPTER_NAME = "Mysql2"
 
@@ -34,11 +35,12 @@ class << self
         def new_client(config)
           ::Mysql2::Client.new(config)
         rescue ::Mysql2::Error => error
-          if error.error_number == ConnectionAdapters::Mysql2Adapter::ER_BAD_DB_ERROR
+          case error.error_number
+          when ER_BAD_DB_ERROR
             raise ActiveRecord::NoDatabaseError.db_error(config[:database])
-          elsif error.error_number == ConnectionAdapters::Mysql2Adapter::ER_ACCESS_DENIED_ERROR
+          when ER_DBACCESS_DENIED_ERROR, ER_ACCESS_DENIED_ERROR
             raise ActiveRecord::DatabaseConnectionError.username_error(config[:username])
-          elsif [ConnectionAdapters::Mysql2Adapter::ER_CONN_HOST_ERROR, ConnectionAdapters::Mysql2Adapter::ER_UNKNOWN_HOST_ERROR].include?(error.error_number)
+          when ER_CONN_HOST_ERROR, ER_UNKNOWN_HOST_ERROR
             raise ActiveRecord::DatabaseConnectionError.hostname_error(config[:host])
           else
             raise ActiveRecord::ConnectionNotEstablished, error.message