feat: working version

1. implemented filesystem storage, NATS object storage
and saving to Vault.
2. Test coverage is fine for filesystem and Vault
(and NATS object does not really require extensive tests)

internal/filesystem/fs_storage_test.go

@@ -7,15 +7,16 @@ import (
 )
 
 func TestStorageMethods(t *testing.T) {
-	st, err := Open("./testdata")
+	st, err := New("./testdata")
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	name := "mytestfile"
-	data := []byte("contents of my test file")
 
-	defer os.Remove(name) // just in case
+	defer os.RemoveAll("./testdata/m")
+
+	data := []byte("contents of my test file")
 
 	if err := st.Save(name, data); err != nil {
 		t.Fatal(err)
@@ -41,5 +42,4 @@ func TestStorageMethods(t *testing.T) {
 	if err := st.Delete(name); err != nil {
 		t.Errorf("delete of non-existent failed: %v", err)
 	}
-
 }