Values:
STATE_UNSPECIFIED (0):
The state is unknown. This is used for API
compatibility only and is not used by the
system.
PENDING (1):
The state was not sampled by the health
checks yet.
OFFLINE (2):
The source was sampled by health checks and
is not available.
FAILED (3):
The source is available but might not be
usable yet due to unvalidated credentials or
another reason. The credentials referred to are
the ones to the Source. The error message will
contain further details.
ACTIVE (4):
The source exists and its credentials were
verified.
