Unified Storage: Search permissions put behind feature flag (#99340)

* add feature flag

* puts search permission filtering behind a feature flag

* fixes issue with doc match id. When the match is for an in-memory index, the internal id is a string (this is what we expected). However, when its a file-based index, the internal id is a binary encoded int64 that point to something internally. So to get the id, we need to use ExternalID() instead of relying on the indexInternalID to be the correct format.

* adds debug log

* update comment

* formatting

pkg/storage/unified/sql/server.go

@@ -70,7 +70,8 @@ func NewResourceServer(ctx context.Context, db infraDB.DB, cfg *setting.Cfg,
 			Root:          root,
 			FileThreshold: int64(cfg.IndexFileThreshold), // fewer than X items will use a memory index
 			BatchSize:     cfg.IndexMaxBatchSize,         // This is the batch size for how many objects to add to the index at once
-		}, tracer)
+		}, tracer, features)
+
 		if err != nil {
 			return nil, err
 		}