feat: support provider-specific OAuth whitelists (#882)

Co-authored-by: Puneet Dixit <236133619+puneetdixit200@users.noreply.github.com>

internal/service/auth_service_test.go

@@ -0,0 +1,39 @@
+package service
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/tinyauthapp/tinyauth/internal/model"
+	"github.com/tinyauthapp/tinyauth/internal/utils/logger"
+)
+
+func TestIsEmailWhitelistedUsesProviderSpecificList(t *testing.T) {
+	log := logger.NewLogger().WithTestConfig()
+	log.Init()
+
+	auth := &AuthService{
+		log: log,
+		runtime: model.RuntimeConfig{
+			OAuthWhitelist: []string{"global@example.com"},
+			OAuthProviders: map[string]model.OAuthServiceConfig{
+				"github": {
+					Whitelist: []string{"github@example.com"},
+				},
+				"pocketid": {
+					Whitelist: []string{"pocket@example.com"},
+				},
+				"gitlab": {
+					Whitelist: []string{},
+				},
+			},
+		},
+	}
+
+	assert.True(t, auth.IsEmailWhitelisted("github", "github@example.com"))
+	assert.False(t, auth.IsEmailWhitelisted("github", "pocket@example.com"))
+	assert.True(t, auth.IsEmailWhitelisted("pocketid", "pocket@example.com"))
+	assert.True(t, auth.IsEmailWhitelisted("google", "global@example.com"))
+	assert.True(t, auth.IsEmailWhitelisted("gitlab", "global@example.com"))
+	assert.False(t, auth.IsEmailWhitelisted("gitlab", "unknown@example.com"))
+}