fix: re-enable expiration_policy for pull subscription, fix push subscription generation with empty expiration_policy

[ktinubu]

• Add back expiration_policy field for pull subscription (mistakenly removed in fix: migrate pull_subscriptions and push_subscriptions to object lists #224)
• update main.tf to correctly handle expiration_policy object fields (pull_subscriptions and push_subscriptions were migrated to object lists in fix: migrate pull_subscriptions and push_subscriptions to object lists #224)

[q2w]

Thanks for the fix!

[apeabody]

Thanks @ktinubu!

Already approved

[Ram1604]

@ktinubu @q2w @apeabody

I couldn't set the expiration policy to 'never expire' for pull subscriptions. But push is working fine.

pull_subscriptions = [
{
name = "test-pull"
ack_deadline_seconds = 30
message_retention_duration = "2000s"
retain_acked_messages = false
dead_letter_topic = null
max_delivery_attempts = null
minimum_backoff = null
maximum_backoff = null
filter = null
enable_message_ordering = true
enable_exactly_once_delivery = true
expiration_policy = ""
}
]

push_subscriptions = [
{
name = "test-push"
ack_deadline_seconds = 20
message_retention_duration = "604800s"
retain_acked_messages = false
push_endpoint = "https://example.com/"
oidc_service_account_email = "svc-parsehub-staging@imgcp-c60779a219ef249c.iam.gserviceaccount.com"
dead_letter_topic = "projects/imgcp-c60779a219ef249c/topics/gds-deals-ingestor-dead-topic"
max_delivery_attempts = 5
maximum_backoff = null
minimum_backoff = null
filter = null
enable_exactly_once_delivery = true
enable_message_ordering = true
expiration_policy = ""
}
]

Expected behavior
expiration_policy = ""

When I use the above in pull subscription, the subscription should not expire.

Observed behavior
Instead, the subscription is getting created as "will expire after 31 days.