backend: refactor backend Connections and HasAtomicReplace into Properties

internal/backend/s3/s3.go

@@ -261,8 +261,11 @@ func (be *Backend) IsPermanentError(err error) bool {
 	return false
 }
 
-func (be *Backend) Connections() uint {
-	return be.cfg.Connections
+func (be *Backend) Properties() backend.Properties {
+	return backend.Properties{
+		Connections:      be.cfg.Connections,
+		HasAtomicReplace: true,
+	}
 }
 
 // Hasher may return a hash function for calculating a content hash for the backend
@@ -270,11 +273,6 @@ func (be *Backend) Hasher() hash.Hash {
 	return nil
 }
 
-// HasAtomicReplace returns whether Save() can atomically replace files
-func (be *Backend) HasAtomicReplace() bool {
-	return true
-}
-
 // Path returns the path in the bucket that is used for this backend.
 func (be *Backend) Path() string {
 	return be.cfg.Prefix