Support for multiple pdbs in ORACLE_DATABASE about oci-oracle-xe

[gvenzl]

Hi @jmichler, actually, starting with 21c, XE no longer has any restrictions on the number of PDBs.

However, ORACLE_DATABASE was not introduced to provide an easy way to provision multiple PDBs at once, or clone from others, etc. It is a variable that allows a user to provide a database name to connect to if for whatever reason XEPDB1 is not good enough.

It falls in line with other images that provide a similar mechanism, like MySQL:

MYSQL_DATABASE
This variable is optional and allows you to specify the name of a database to be created on image startup. If a user/password was supplied (see below) then that user will be granted superuser access (corresponding to GRANT ALL) to this database.

Or Postgres:

POSTGRES_DB
This optional environment variable can be used to define a different name for the default database that is created when the image is first started. If it is not specified, then the value of POSTGRES_USER will be used.

If a user wants to provision multiple PDBs, the initialization scripts mechanism should be used instead. This also allows the user to create additional database users, grant privileges on those PDBs to them, and much more.