srvEntitiesWatcher defines the API for methods on a state.StringsWatcher.
Each client has its own current set of watchers, stored in resources.
srvEntitiesWatcher notifies about changes for all entities of a given kind,
sending the changes as a list of strings, which could be transformed
from state entity ids to their corresponding entity tags.
Next returns when a change has occurred to an entity of the
collection being watched since the most recent call to Next
or the Watch call that created the srvEntitiesWatcher.
srvEntitiesWatcher defines the API for methods on a state.StringsWatcher. Each client has its own current set of watchers, stored in resources. srvEntitiesWatcher notifies about changes for all entities of a given kind, sending the changes as a list of strings, which could be transformed from state entity ids to their corresponding entity tags.