storage: persist API server URL alongisde Account details (#14)

This commit adds the functionality that stores the acme-dns API URL alongisde of the rest of the account information. The account information is dependant of the API server in question, so at least for me it makes sense.

The new functionality allows the storage to be self sufficient for all the required data points. While the API server URL can often be deducted from the account URL, it's not guaranteed.

This commit also adds a test to ensure backwards compatibility with old storage format and to mitigate potential regressions in the backwards compatibility in the future.

account.go

@@ -8,4 +8,7 @@ type Account struct {
 	SubDomain  string `json:"subdomain"`
 	Username   string `json:"username"`
 	Password   string `json:"password"`
+	// ServerURL contains the URL of the acme-dns server the Account was registered with
+	// (may be empty for Account instances registered before this field was added).
+	ServerURL string `json:"server_url"`
 }

client.go

@@ -167,6 +167,8 @@ func (c Client) RegisterAccount(allowFrom []string) (Account, error) {
 		return Account{}, fmt.Errorf("Failed to unmarshal account: %w", err)
 	}
 
+	acct.ServerURL = c.baseURL
+
 	return acct, nil
 }
 

client_test.go

@@ -116,6 +116,8 @@ func TestRegisterAccount(t *testing.T) {
 					t.Errorf("expected err %#v, got %#v\n", tc.ExpectedErr, err)
 				}
 			} else if tc.ExpectedErr == nil && err == nil {
+				// Needed to be able to assert equivalence, as the server addr is dynamic
+				tc.ExpectedAccount.ServerURL = acct.ServerURL
 				if !reflect.DeepEqual(acct, *tc.ExpectedAccount) {
 					t.Errorf("expected account %v, got %v\n", tc.ExpectedAccount, acct)
 				}

storage_test.go

@@ -15,7 +15,18 @@ var testAccounts = map[string]Account{
 		SubDomain:  "tossed.lettuceencrypt.org",
 		Username:   "cpu",
 		Password:   "hunter2",
+		ServerURL:  "https://auth.acme-dns.io",
 	},
+	"threeletter.agency": {
+		FullDomain: "threeletter.agency",
+		SubDomain:  "jobs.threeletter.agency",
+		Username:   "spooky.mulder",
+		Password:   "trustno1",
+		ServerURL:  "https://example.org",
+	},
+}
+
+var testLegacyAccount = map[string]Account{
 	"threeletter.agency": {
 		FullDomain: "threeletter.agency",
 		SubDomain:  "jobs.threeletter.agency",
@@ -79,6 +90,66 @@ func TestNewFileStorage(t *testing.T) {
 	}
 }
 
+func TestNewFileStorageWithLegacyData(t *testing.T) {
+	mode := os.FileMode(0600)
+
+	var (
+		legacyAcct, testAcct Account
+		found                bool
+	)
+
+	testData, err := json.Marshal(testLegacyAccount)
+	if err != nil {
+		t.Fatalf("unexpected error marshaling testAccounts: %v", err)
+	}
+
+	f, err := ioutil.TempFile("", "legacy.account")
+	if err != nil {
+		t.Errorf("unexpected error creating tempfile: %v", err)
+	}
+
+	defer func() { _ = f.Close() }()
+
+	_, err = f.Write(testData)
+	if err != nil {
+		t.Errorf("unexpected error writing to tempfile: %v", err)
+	}
+
+	storage := NewFileStorage(f.Name(), mode)
+
+	fs, ok := storage.(fileStorage)
+	if !ok {
+		t.Fatalf("expected fileStorage instance from NewFileStorage, got %T", storage)
+	}
+
+	if fs.accounts == nil {
+		t.Fatalf("expected accounts to be not-nil, was nil")
+	}
+
+	if len(fs.accounts) != 1 {
+		t.Fatalf("expected a single account in the map, got %d", len(fs.accounts))
+	}
+
+	if legacyAcct, found = fs.accounts["threeletter.agency"]; !found {
+		t.Fatalf("expected to find account but was unable to")
+	}
+
+	if legacyAcct.ServerURL != "" {
+		t.Errorf("expected empty Server string from legacy account, but got %s", legacyAcct.ServerURL)
+	}
+
+	if testAcct, found = testAccounts["threeletter.agency"]; !found {
+		t.Fatalf("expected to find test account for threeletter.agency, but was unable to")
+	}
+
+	// set the missing value for legacy account to be able to evaluate equivalence
+	legacyAcct.ServerURL = testAcct.ServerURL
+
+	if !reflect.DeepEqual(legacyAcct, testAcct) {
+		t.Errorf("expected equivalent test and legacy accounts")
+	}
+}
+
 func TestFileStorageSave(t *testing.T) {
 	f, err := ioutil.TempFile("", "acmedns.account")