mysql credentials config

[Huahan98]

Change username and password in ./Autolab/config/database.yml according to the credentials user provided in docker-compose.yml (as part of the make command), so there is only one file that the user needs to change without having to navigate to the Autolab submodule.

How to test:

1. checkout docker-mysql-credentials branch in Autolab
2. change MYSQL_USER and MYSQL_PASSWORD in docker-compose.yml to customized credentials
3. make clean && make, check that ./Autolab/config/database.yml has the right credentials

[fanpu]

I changed MYSQL_USER to fanpu and I am getting the following when trying to connect to the db from within the Autolab container:

root@9350bb0fe99f:/home/app/webapp# RAILS_ENV=production bundle exec rails c
Loading production environment (Rails 5.2.0)
2.6.6 :001 > User.first
Traceback (most recent call last):
        1: from (irb):1
Mysql2::Error (Access denied for user 'fanpu'@'172.18.0.6' (using password: YES))

When I dumped the users from the mysql container it looks like the new user was not created:

mysql> SELECT user FROM mysql.user;
+------------------+
| user             |
+------------------+
| user             |
| healthchecker    |
| mysql.infoschema |
| mysql.session    |
| mysql.sys        |
| root             |
+------------------+
6 rows in set (0.00 sec)

It seems like we need to make the MySQL docker aware of these new changes somehow, is there a way of doing that?