Allow testcontainers to be used in development #4764

[jmiranda]

I've used this Gradle configuration to successfully start openboxes in development mode using a testcontainer. But I haven't had a chance to test whether the configuration has any side effects

• do development mode (grails run-app) still run ok with this
• do tests continue to work properly?
• is this the best way to handle this? or is there a better way to scope the dependency so it doesn't need to be included twice?