[rds] Add waiter for cluster actions

Waiters are only implemented for single instance RDS actions, not actions that target Aurora clusters. Can you pleased add them for the following equivalent cluster actions?

db_cluster_available
db_cluster_deleted
db_cluster_snapshot_available
db_cluster_snapshot_completed
db_cluster_snapshot_deleted

Of these we most care about the snapshots, but it would be nice to have all of them implemented.

[tbastos]

+1 ! In our case we need db_cluster_available

[edvegas]

I had to implement my own waiter to solve this (example for 200 attempts with 30 seconds timeout):

def wait_until_db_cluster_ready(db_cluster_name):

    try:
        rds_client = boto3.client('rds')

        time.sleep(30) # this is added because sometimes cluster status not updated immediately when you modify it

        for cycles in range(0, 200):
            cluster_status_request = rds_client.describe_db_clusters(
                DBClusterIdentifier=db_cluster_name,
            )
            if (cluster_status_request['DBClusters'][0]['Status'] == 'available'):
                break
            else:
                cycles = cycles + 1
                time.sleep(30)

    except Exception as e:
        log(
            f"An error occurred trying to get db cluster status, exiting the script. Error: { e }")
        sys.exit(1)

and then call it when necessary wait_until_db_cluster_ready('my_cluster')