Backend: Expose connections parameter

internal/restic/backend.go

@@ -18,6 +18,9 @@ type Backend interface {
 	// repository.
 	Location() string
 
+	// Connections returns the maxmimum number of concurrent backend operations.
+	Connections() uint
+
 	// Hasher may return a hash function for calculating a content hash for the backend
 	Hasher() hash.Hash