Values:
STATE_UNSPECIFIED (0):
Workflow state is unspecified.
DRAFT (1):
Workflow is in draft status, i.e. tasks are
not yet eligible for execution.
RUNNING (2):
Workflow is running (i.e. tasks are eligible
for execution).
PAUSED (3):
Workflow is paused. Tasks currently in
progress may continue, but no further tasks will
be scheduled.
COMPLETED (4):
Workflow is complete. There should not be any
task in a non-terminal state, but if they are
(e.g. forced termination), they will not be
scheduled.
