Allow to trigger a deployment if another one is already ongoing on the same environment (queue deployments)

Today you can trigger only one deployment at a time within one environment. If a deployment is ongoing on the environment and you try to trigger a second deployment, you will get an error message telling you that the operation is not allowed (since another deployment is ongoing)
The objective will be to allow you to trigger other deployments if there's one already ongoing. At the minimum we will provide the possibility to queue the deployments without having you wait for the deployment to end, improvements could be done in the future to parallelize the operations (if the deployment is not on the same service)