Set `AUTO_DEVOPS_POSTGRES_MANAGED` to `true` if Crossplane is installed
Follow-up from introducing Crossplane to GitLab managed apps as suggested by @tkuah .
When Crossplane is installed via GitLab managed apps, presumably the user is interested in having the database instance provisioned and managed by Crossplane. For that the user would have to set
true, which could already be done automatically during the pipeline run.
Although, this could be risky. If we have a group cluster with Crossplane installed, setting this variable to true would make all children projects to have one database instance provisioned per branch. That could be super costly depending on the number of projects.