The mutable client registry carried as the store's extraArgument.
configureStore captures this object by reference, so slots added after the
store is built are visible to every subsequent request. That is what allows a
second client to attach itself to a store it did not create.
The mutable client registry carried as the store's
extraArgument.configureStorecaptures this object by reference, so slots added after the store is built are visible to every subsequent request. That is what allows a second client to attach itself to a store it did not create.