Retrieves existing shareable links for a shipment.

When accessLevel is provided, returns only the link for that access level (0 or 1 results).
When omitted, returns all links for the shipment across all access levels.

accessLevel values:

• LocationOnly — viewers can see shipment location only
• ConditionOnly — viewers can see sensor/condition data only
• LocationAndCondition — viewers can see both location and sensor data