[#417] storagegroup: Mark all expiration methods as deprecated

`expiration_epoch` field of `StorageGroup` message has been marked as
deprecated in previous NeoFS API protocol's release.

Mark all method related to the field as deprecated. Leave and use them
for test purposes only.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

storagegroup/convert.go

@@ -15,6 +15,7 @@ func (s *StorageGroup) ToGRPCMessage() grpc.Message {
 		m = new(sg.StorageGroup)
 
 		m.SetMembers(refs.ObjectIDListToGRPCMessage(s.members))
+		//nolint:staticcheck
 		m.SetExpirationEpoch(s.exp)
 		m.SetValidationDataSize(s.size)
 		m.SetValidationHash(s.hash.ToGRPCMessage().(*refsGRPC.Checksum))

storagegroup/grpc/types.go

@@ -15,6 +15,8 @@ func (m *StorageGroup) SetValidationHash(v *refs.Checksum) {
 }
 
 // SetExpirationEpoch sets number of the last epoch of the storage group lifetime.
+//
+// Deprecated: do not use, `expiration_epoch` field is deprecated in protocol.
 func (m *StorageGroup) SetExpirationEpoch(v uint64) {
 	m.ExpirationEpoch = v
 }

storagegroup/test/generate.go

@@ -10,6 +10,7 @@ func GenerateStorageGroup(empty bool) *storagegroup.StorageGroup {
 
 	if !empty {
 		m.SetValidationDataSize(44)
+		//nolint:staticcheck
 		m.SetExpirationEpoch(55)
 		m.SetMembers(refstest.GenerateObjectIDs(false))
 	}

storagegroup/types.go

@@ -45,6 +45,8 @@ func (s *StorageGroup) SetValidationHash(v *refs.Checksum) {
 }
 
 // GetExpirationEpoch of unified storage group structure.
+//
+// Deprecated: Do not use.
 func (s *StorageGroup) GetExpirationEpoch() uint64 {
 	if s != nil {
 		return s.exp
@@ -54,6 +56,8 @@ func (s *StorageGroup) GetExpirationEpoch() uint64 {
 }
 
 // SetExpirationEpoch into unified storage group structure.
+//
+// Deprecated: Do not use.
 func (s *StorageGroup) SetExpirationEpoch(v uint64) {
 	s.exp = v
 }