/usr/include/saml/saml2/metadata/ is in libsaml2-dev 2.5.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/saml/saml2/metadata/AbstractMetadataProvider.h
/usr/include/saml/saml2/metadata/DiscoverableMetadataProvider.h
/usr/include/saml/saml2/metadata/DynamicMetadataProvider.h
/usr/include/saml/saml2/metadata/EndpointManager.h
/usr/include/saml/saml2/metadata/EntityMatcher.h
/usr/include/saml/saml2/metadata/Metadata.h
/usr/include/saml/saml2/metadata/MetadataCredentialContext.h
/usr/include/saml/saml2/metadata/MetadataCredentialCriteria.h
/usr/include/saml/saml2/metadata/MetadataFilter.h
/usr/include/saml/saml2/metadata/MetadataProvider.h
/usr/include/saml/saml2/metadata/ObservableMetadataProvider.h