Represents the different states of a AppConnection.
Values:
STATE_UNSPECIFIED (0):
Default value. This value is unused.
CREATING (1):
AppConnection is being created.
CREATED (2):
AppConnection has been created.
UPDATING (3):
AppConnection's configuration is being
updated.
DELETING (4):
AppConnection is being deleted.
DOWN (5):
AppConnection is down and may be restored in
the future. This happens when CCFE sends
ProjectState = OFF.
