[Enhancement]: Expose `compatibleSubstituteFor()` through API

Module

Core

Proposal

I would like to allow unversioned images like wiremock/wiremock:test if and only if compatibleSubstituteFor is explicitly set by the users. By default, IMHO the validation should fail, because we cannot compare against the minimum required version.

At the moment it is not possible, because there is no getter method for compatibleSubstituteFor

Sample code

    public WireMockContainer(DockerImageName dockerImage) {
        super(dockerImage);
        dockerImage.assertCompatibleWith(new DockerImageName(OFFICIAL_IMAGE_NAME));

        // Verify the minimum version for the official image
        final ComparableVersion version = new ComparableVersion(dockerImage.getVersionPart());
        if (!version.isSemanticVersion()) { // Accept only images when compatibility is declared explicitly
            // TODO: We cannot extract compatibleSubstituteFor from Testcontainers API
        } else {
            boolean isLessThanBaseVersion = version.isLessThan(WIREMOCK_2_MINIMUM_SUPPORTED_VERSION);
            if (OFFICIAL_IMAGE_NAME.equals(dockerImage.getUnversionedPart()) && isLessThanBaseVersion) {
                throw new IllegalArgumentException("For the official image, the WireMock version must be >= " + WIREMOCK_2_MINIMUM_SUPPORTED_VERSION);
            }
        }

      // ...

Sample Test

    @Test
    @Disabled("Requires https://github.com/testcontainers/testcontainers-java/issues/7305")
    public void shouldFailForUnversionedImage() {
        IllegalStateException ex = Assertions.assertThrows(IllegalStateException.class, () -> {
            WireMockContainer container = new WireMockContainer(
                    new DockerImageName(WireMockContainer.OFFICIAL_IMAGE_NAME, "test"));
        });
        assertThat(ex.getMessage())
                .as("Wrong exception message")
                .contains("Failed to verify that image")
                .contains("is a compatible substitute for '" + WireMockContainer.OFFICIAL_IMAGE_NAME + "'");
    }

Start with the DockerImageName and compatibleSubstituteFor/assertCompatibleWith API paths shown in the issue, then locate their related tests. Expose the explicitly configured compatible substitute and enable the disabled WireMockContainer test once it can verify the expected failure message.