Check team permissions on bulk APIs for Connections, Variables and Pools

[vincbeck]

When creating/updating connections, variables or pools through the bulk API, we currently no not check whether the user has access to team passed in the request body. Adding it now.

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[ramitkataria]

I think existing_team_name will always be None here. The callers build the team mapping dict from a list that's filtered with if action.action != BulkAction.CREATE (e.g., line 449 for pools), which excludes all CREATE actions, including CREATE-with-overwrite. So the .get() call that populates existing_team_name never finds the key.

I believe the filters for pools, connections and variables need to also include CREATE-with-overwrite entities, something like:

if action.action != BulkAction.CREATE or action.action_on_existence == BulkActionOnExistence.OVERWRITE