[#1402] pkg: Move SGSource to the core directory

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/core/storagegroup/storagegroup.go

@@ -0,0 +1,48 @@
+package storagegroup
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/core/client"
+	"github.com/nspcc-dev/neofs-sdk-go/container/id"
+	"github.com/nspcc-dev/neofs-sdk-go/netmap"
+	"github.com/nspcc-dev/neofs-sdk-go/object/id"
+	"github.com/nspcc-dev/neofs-sdk-go/storagegroup"
+)
+
+// SearchSGPrm groups the parameters which are formed by Processor to search the storage group objects.
+type SearchSGPrm struct {
+	Context context.Context
+
+	Container cid.ID
+
+	NodeInfo client.NodeInfo
+}
+
+// SearchSGDst groups the target values which Processor expects from SG searching to process.
+type SearchSGDst struct {
+	Objects []oid.ID
+}
+
+// GetSGPrm groups parameter of GetSG operation.
+type GetSGPrm struct {
+	Context context.Context
+
+	OID oid.ID
+	CID cid.ID
+
+	NetMap    netmap.NetMap
+	Container [][]netmap.NodeInfo
+}
+
+// SGSource is a storage group information source interface.
+type SGSource interface {
+	// ListSG must list storage group objects in the container. Formed list must be written to destination.
+	//
+	// Must return any error encountered which did not allow to form the list.
+	ListSG(*SearchSGDst, SearchSGPrm) error
+
+	// GetSG must return storage group object for the provided CID, OID,
+	// container and netmap state.
+	GetSG(GetSGPrm) (*storagegroup.StorageGroup, error)
+}