feat(example): Allow configuring some parameters with env variables (#663)

Co-authored-by: Andrey Rusakov <andrey.rusakov@camptocamp.com>

example/server/storage/user.go

@@ -2,6 +2,8 @@ package storage
 
 import (
 	"crypto/rsa"
+	"encoding/json"
+	"os"
 	"strings"
 
 	"golang.org/x/text/language"
@@ -35,6 +37,18 @@ type userStore struct {
 	users map[string]*User
 }
 
+func StoreFromFile(path string) (UserStore, error) {
+	users := map[string]*User{}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	if err := json.Unmarshal(data, &users); err != nil {
+		return nil, err
+	}
+	return userStore{users}, nil
+}
+
 func NewUserStore(issuer string) UserStore {
 	hostname := strings.Split(strings.Split(issuer, "://")[1], ":")[0]
 	return userStore{

example/server/storage/user_test.go

@@ -0,0 +1,70 @@
+package storage
+
+import (
+	"os"
+	"path"
+	"reflect"
+	"testing"
+
+	"golang.org/x/text/language"
+)
+
+func TestStoreFromFile(t *testing.T) {
+	for _, tc := range []struct {
+		name       string
+		pathToFile string
+		content    string
+		want       UserStore
+		wantErr    bool
+	}{
+		{
+			name:       "normal user file",
+			pathToFile: "userfile.json",
+			content: `{
+				"id1": {
+					"ID":                "id1",
+					"EmailVerified":     true,
+					"PreferredLanguage": "DE"
+				}
+			}`,
+			want: userStore{map[string]*User{
+				"id1": {
+					ID:                "id1",
+					EmailVerified:     true,
+					PreferredLanguage: language.German,
+				},
+			}},
+		},
+		{
+			name:       "malformed file",
+			pathToFile: "whatever",
+			content:    "not a json just a text",
+			wantErr:    true,
+		},
+		{
+			name:       "not existing file",
+			pathToFile: "what/ever/file",
+			wantErr:    true,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			actualPath := path.Join(t.TempDir(), tc.pathToFile)
+
+			if tc.content != "" && tc.pathToFile != "" {
+				if err := os.WriteFile(actualPath, []byte(tc.content), 0666); err != nil {
+					t.Fatalf("cannot create file with test content: %q", tc.content)
+				}
+			}
+			result, err := StoreFromFile(actualPath)
+			if err != nil && !tc.wantErr {
+				t.Errorf("StoreFromFile(%q) returned unexpected error %q", tc.pathToFile, err)
+			} else if err == nil && tc.wantErr {
+				t.Errorf("StoreFromFile(%q) did not return an expected error", tc.pathToFile)
+			}
+			if !tc.wantErr && !reflect.DeepEqual(tc.want, result.(userStore)) {
+				t.Errorf("expected StoreFromFile(%q) = %v, but got %v",
+					tc.pathToFile, tc.want, result)
+			}
+		})
+	}
+}