enhancement: Easier configuration of the postgres command

[KyleAure]

Currently, the PostgreSQLContainer configures fync=off during initialization of the container class.
This setting can be accidentally overwritten by using the withCommand() or setCommand() methods.
It would be more extensible to keep a list of configuration options for the postgres command, and instead configure a command during the configure lifecycle step.

Opening this PR because this is how I use the PostgreSQL container and thought maybe others might find this useful.
If there is no interest feel free to close this PR.

[richardfearn]

Slightly related to #938

[richardfearn]

I would also love a way to do this via the JDBC URL. The 'best' option I've come up with so far is a new TC_ (container) parameter for a list of comma-separated, URL-encoded, additional command-line options to add to the command. The configure method in PostgreSQLContainer can then split/decode them and append them to the command.

The URL could look something like this, for example:

jdbc:tc:postgresql:15.10:///integration_tests?TC_INITSCRIPT=initPostgres.sql&TC_COMMAND_EXTRA=-c,log_statement%3Dall

[KyleAure]

@richardfearn Thanks for posting an alternative option for others.
Unfortunately, for many of my complex test cases I cannot use the Testcontainer based JDBC URL.

[eddumelendez]

Thanks for your contribution, @KyleAure. I think would be nice to add this to the GenericContainer instead. So, every implementation get benefit of it.

@richardfearn for more complex scenarios it is recommended to move from Testcontainers JDBC URL to PostgreSQLContainers.

[KyleAure]

@eddumelendez

I think would be nice to add this to the GenericContainer instead. So, every implementation get benefit of it.

I believe that the GenericContainer already has an option for this which would be withCommand.
The reason we an additional configuration method in Postgres is because we need to configure both a default option fsync=off AND to allow users of the container object the ability to add additional command options.

I don't know how much value other containers would have for such a method, and any container that would want that functionality would still need to itself define the default command, and any default options.
Therefore, adding this to the GenericContainer would still require refactoring of individual container classes to be able to implement the use case.