Allow to set protected file patterns that can not be changed under no conditions (#10806)

Co-Authored-By: zeripath <art27@cantab.net>

modules/auth/repo_form.go

@@ -175,6 +175,7 @@ type ProtectBranchForm struct {
 	BlockOnRejectedReviews   bool
 	DismissStaleApprovals    bool
 	RequireSignedCommits     bool
+	ProtectedFilePatterns    string
 }
 
 // Validate validates the fields