http://hl7.org/fhir/StructureDefinition/capabilitystatement-search-parameter-combination|5.2.0

This extension defines a possible search parameter combination by listing a set of search parameters and indicating whether they are required or optional.\n- If a search combination is specified, clients should expect that they must submit a search that meets one of the required combinations or the search will be unsuccessful.\n- If multiple search parameter combinations are specified, a client may pick between them, and supply the minimal required parameters for any of the combinations.\n- If no parameters in the set of search parameters are listed as required, then *at least one* of the listed optional parameters must be present. This shorthand method is the same as repeating the entire extension for each combination of optional and required search parameters.