collection_mutation: add a FIXME.
collection_mutation: add a FIXME.

We could use iterators over cells instead of a vector of cells
in collection_mutation(_view)_description. Then some use cases could
provide iterators that construct the cells "on the fly".

avikivity/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla