add DB_ADMIN_USER to support postgresql docker

[hieplq]

if use postgresql docker we can define a user difference postgres as superUser
so beside DB_ADMIN_PASS then DB_ADMIN_USER should add as environment variable

[hieplq]

custom name for super user isn't support by idempiere itself
so console-setup will not pass

can overcome by on docker create empty database before run console-setup

[CarlosRuiz-globalqss]

@hieplq - the commits idempiere/idempiere@28171cda and idempiere/idempiere@2e7f2cdb can be an example about how it can be done, there is hardcoded for amazon, but maybe is not too hard to make it more generic.

[hieplq]

"create empty database before run console-setup" is a workaround
to fix it also fix for amazon case maybe we add DB_ADMIN_USER with default = postgres to setup (dialog also command line)

[hsahmed]

We should make the creation of the database optional for Docker containers or console-setup. This would also remove the need to customize the installation code for managed databases like AWS RDS or Azure Database for Postgresql.