The alias was only ever used to build the `include_labels` filter on the generated vector source, while dokku labels containers with `com.dokku.app-name` unconditionally. Setting the property therefore pointed the source at a label no container carries, and log collection stopped without any error. The source now always filters the label dokku applies, and a generated remap renames the field on its way to the sink, which is what the property was documented to do. An app whose own alias differs from the global one gets a branch in the global pipeline, so a per-app value is honored even when the app ships through the global sink.
Closes#8916.
5b5d3d761b