This class represents a session with the local File Service. A session
corresponds to a single HttpRequest to the Dev App Server. The significance
of a session is the following:
- A session is the scope for a lock. That is, at most one session may own
the lock on a file at a time.
- A file is Opened relative to a session. That is the Open state of a file
is defined relative to a particular session.
- Files opened in a session are automatically closed at the end of the
session, which is the end of the HttpRequest.