Customize the Bundle in FHIR search responses

[qligier]

Would it be possible to customize the Bundle in FHIR search responses? E.g. in ITI-78, ITI-66, ITI-67

With the IBundleProvider, it's only possible to return a list of resources, which prevents setting Bundle.entry.search.mode. Also, when adding OperationOutcomes to the list, they are counted in the Bundle.total, but should not (Bundle.total: It does not include search.mode = 'include' or 'outcome' entries).