When this subscription should send messages to subscribers relative
to messages persistence in storage. For details, see Creating Lite
subscriptions <https://cloud.google.com/pubsub/lite/docs/subscriptions#creating_lite_subscriptions>__.
Values:
DELIVERY_REQUIREMENT_UNSPECIFIED (0):
Default value. This value is unused.
DELIVER_IMMEDIATELY (1):
The server does not wait for a published
message to be successfully written to storage
before delivering it to subscribers.
DELIVER_AFTER_STORED (2):
The server will not deliver a published
message to subscribers until the message has
been successfully written to storage. This will
result in higher end-to-end latency, but
consistent delivery.
