Message handling

The states handle the messages as follows:

• RUNNING state: Handles the STORAGE_CLEAR, STORAGE_FLUSH, STORAGE_STATS, and STORAGE_SET_THRESHOLD messages.
• BUFFER_IDLE state: Handles STORAGE_BATCH_REQUEST to transition to BUFFER_PIPE_ACTIVE.
• BUFFER_PIPE_ACTIVE state: Populates the pipe with [header + data] items and handles the session management.