[#1461] engine: Clarify force removal

Document force removal behaviour in all the Storage engine parts.

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

pkg/local_object_storage/engine/delete.go

@@ -42,6 +42,10 @@ func (p *DeletePrm) WithForceRemoval() {
 //
 // Returns apistatus.ObjectLocked if at least one object is locked.
 // In this case no object from the list is marked to be deleted.
+//
+// NOTE: Marks any object to be deleted (despite any prohibitions
+// on operations with that object) if WithForceRemoval option has
+// been provided.
 func (e *StorageEngine) Delete(prm DeletePrm) (res DeleteRes, err error) {
 	err = e.execIfNotBlocked(func() error {
 		res, err = e.delete(prm)

pkg/local_object_storage/engine/inhume.go

@@ -61,6 +61,9 @@ var errInhumeFailure = errors.New("inhume operation failed")
 // Allows inhuming non-locked objects only. Returns apistatus.ObjectLocked
 // if at least one object is locked.
 //
+// NOTE: Marks any object as removed (despite any prohibitions on operations
+// with that object) if WithForceRemoval option has been provided.
+//
 // Returns an error if executions are blocked (see BlockExecution).
 func (e *StorageEngine) Inhume(prm InhumePrm) (res InhumeRes, err error) {
 	err = e.execIfNotBlocked(func() error {

pkg/local_object_storage/metabase/inhume.go

@@ -100,7 +100,11 @@ var ErrLockObjectRemoval = errors.New("lock object removal")
 // Inhume marks objects as removed but not removes it from metabase.
 //
 // Allows inhuming non-locked objects only. Returns apistatus.ObjectLocked
-// if at least one object is locked.
+// if at least one object is locked. Returns ErrLockObjectRemoval if inhuming
+// is being performed on lock (not locked) object.
+//
+// NOTE: Marks any object with GC mark (despite any prohibitions on operations
+// with that object) if WithForceGCMark option has been provided.
 func (db *DB) Inhume(prm InhumePrm) (res InhumeRes, err error) {
 	err = db.boltDB.Update(func(tx *bbolt.Tx) error {
 		garbageBKT := tx.Bucket(garbageBucketName)