Limit Fivetran task concurrency so it only tries to run one sync per connector at a time. (#5083)

bigquery_etl/query_scheduling/templates/airflow_dag.j2

@@ -383,6 +383,7 @@ with DAG('{{ name }}', default_args=default_args{%+ if schedule_interval != None
     {{ fivetran_task.task_id }}_sync_start = FivetranOperator(
         connector_id='{% raw %}{{ var.value.{% endraw %}{{ fivetran_task.task_id }}{% raw %}_connector_id }}{% endraw %}',
         task_id='{{ fivetran_task.task_id }}_task',
+        task_concurrency=1,
     )
 
     {% do fivetran_seen.append(fivetran_task) %}

tests/data/dags/simple_test_dag

@@ -63,6 +63,7 @@ with DAG(
     fivetran_import_1_sync_start = FivetranOperator(
         connector_id="{{ var.value.fivetran_import_1_connector_id }}",
         task_id="fivetran_import_1_task",
+        task_concurrency=1,
     )
 
     test__non_incremental_query__v1.set_upstream(fivetran_import_1_sync_start)
@@ -70,6 +71,7 @@ with DAG(
     fivetran_import_2_sync_start = FivetranOperator(
         connector_id="{{ var.value.fivetran_import_2_connector_id }}",
         task_id="fivetran_import_2_task",
+        task_concurrency=1,
     )
 
     test__non_incremental_query__v1.set_upstream(fivetran_import_2_sync_start)