after_method_id is too aggressive a dependency.
after_path_and_method_id is marginally better, but is bad practice
nevertheless, as such activity dependencies remain very hard to introspect.
Tags allow more variations, and are hence easier to follow.
Also, add XXX comments when (recursive) reindexation is only added to
represent the dependency, without certainty that a reindexation is actually
needed per-se: maybe another place in the code chould just appropriately
tag its reindexation activities instead, saving at least the cost of
spawning one more activity set, and at most the cost of actually
reindexing these documents.