[DevServices] TestContainers registry configuration

[Xendar]

Description

Hello,

I am currently working on putting in place a database in my project, and I am planning to leverage on DevServices great feature for having my local DB fired up upon a quarkus:dev/quarkusDev on my local Desktop.
It works fine for now, but I have a constraint: We have a private registry from which we need to pull the Docker images.

So I have 2 use cases to manage:

1. The mariadb image
2. the testcontainers/ryuk image

---

For 1., going through the documentation I can simply override the image in my application.yml file:

quarkus:
  datasource:
    db-kind: mariadb
    devservices:
      image-name: mycompany.com/my-registry/mariadb:10.5.9

Pros: Nice & easy!
Cons: In case the MariaDB image version is updated internally by Quarkus, then I won't benefit from this 😢

---

For 2., going through the TestContainers documentation, the recommended way is to leverage on the image name suibstitution to automatically prefix any image with the provided private registry

I tried to use first the environment variable TESTCONTAINERS_HUB_IMAGE_NAME_PREFIX setup, but I was not able somehow to make it available to the Gradle quarkusDev task, I feel like this is not possible today. This is working though with the Maven plugin with the standard confifuration/environmentVariables element.
So I looked at the other way by creating a testcontainers.properties file. The file is usually put in the src/test/resources, but to make it work for DevServices I had to put it in the src/main/resources instead

Pros: I really like the idea of applying a prefix instead of overriding the whole image definition!
Cons: I end up having a configuration file used for development in my production jar

Implementation ideas

1. On Quarkus side, what about putting in place the concept of image name substitution, as having a private registry is quite a common case?
2. Adding the capability in the Gradle plugin to inject environment/system variables to the quarkusDev task
3. Ideally, having a way to store configuration files dedicated to DevServices outside of src/main/resources?

[quarkus-bot]

/cc @stuartwdouglas

[Eng-Fouad]

See #32662