The supported database versions, which are available also with templates, are PostGreSQL and MySQL.
Other like Oracle and MSSQL are not available inside of the pod/project.
But there are Environment Variables to configure that datasources.
Also a description how to add the driver for this is not available.

An example is this (for H2 but it can be used for others as well to create the DS):
The way to configure it is with env-var like this:
DATASOURCES=ACCOUNTS_H2
ACCOUNTS_H2_DATABASE=accounts
ACCOUNTS_H2_JNDI=java:/accounts-ds
ACCOUNTS_H2_DRIVER=h2
ACCOUNTS_H2_JTA=true
ACCOUNTS_H2_NONXA=true
ACCOUNTS_H2_USERNAME=sa
ACCOUNTS_H2_PASSWORD=sa
ACCOUNTS_H2_URL="jdbc:h2:/opt/eap/standalone/data/databases/h2/accounts"

1. required, but unused...
   ACCOUNTS_H2_SERVICE_HOST=dummy
   ACCOUNTS_H2_SERVICE_PORT=12345