searchAllRelatedItems   
  Searches for related items across all cases within a domain. This is a global search operation that returns related items from multiple cases, unlike the case-specific SearchRelatedItems API.
Use cases
Following are common uses cases for this API:
- Find cases with similar issues across the domain. For example, search for all cases containing comments about "product defect" to identify patterns and existing solutions. 
- Locate all cases associated with specific contacts or orders. For example, find all cases linked to a contactArn to understand the complete customer journey. 
- Monitor SLA compliance across cases. For example, search for all cases with "Active" SLA status to prioritize remediation efforts. 
Important things to know
- This API returns case IDs, not complete case objects. To retrieve full case details, you must make additional calls to the GetCase API for each returned case ID. 
- This API searches across related items content, not case fields. Use the SearchCases API to search within case field values. 
Endpoints: See Amazon Connect endpoints and quotas.