Add Gmail API injection, provider presets, delivery method, and frontend wizard

- Add gmail_service.py with Gmail API users.messages.insert() for direct email injection
- Add DeliveryMethod enum and GmailCredential model to database models
- Add delivery_method field to MailAccount schema and model
- Create providers.py endpoint with 12 provider presets (Gmail, GMX, WEB.DE, Outlook, Yahoo, AOL, T-Online, 1&1/IONOS, Freenet, Posteo, mail.de, iCloud)
- Expand MailServerAutoDetect with 30+ domain mappings
- Update Celery tasks to prefer Gmail API injection, with SMTP fallback
- Add ProviderWizard.tsx frontend component for quick provider setup
- Update AddMailAccountModal.tsx with wizard integration
- Add Google API Python client libraries to requirements.txt
- Add Gmail API config settings
- Add unit tests for Gmail service and provider presets

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
Agent-Logs-Url: https://github.com/christianlouis/pop_puller_to_gmail/sessions/de3ef930-a980-4958-8a9d-a2c802918e81

backend/tests/unit/test_gmail_service.py

@@ -0,0 +1,152 @@
+"""
+Unit tests for Gmail service module.
+"""
+import pytest
+from unittest.mock import MagicMock, patch, AsyncMock
+from app.services.gmail_service import GmailService, GmailInjectionError, GMAIL_SCOPES
+
+
+class TestGmailService:
+    """Test Gmail API service"""
+
+    def test_gmail_scopes(self):
+        """Test that required Gmail scopes are defined"""
+        assert "https://www.googleapis.com/auth/gmail.insert" in GMAIL_SCOPES
+        assert "https://www.googleapis.com/auth/gmail.labels" in GMAIL_SCOPES
+
+    def test_init_creates_credentials(self):
+        """Test that GmailService initializes with credentials"""
+        service = GmailService(
+            access_token="test-access-token",
+            refresh_token="test-refresh-token",
+            client_id="test-client-id",
+            client_secret="test-client-secret",
+        )
+
+        assert service.credentials is not None
+        assert service.credentials.token == "test-access-token"
+        assert service.credentials.refresh_token == "test-refresh-token"
+        assert service.credentials.client_id == "test-client-id"
+        assert service.credentials.client_secret == "test-client-secret"
+
+    def test_init_without_refresh_token(self):
+        """Test initialization without refresh token"""
+        service = GmailService(access_token="test-access-token")
+
+        assert service.credentials is not None
+        assert service.credentials.token == "test-access-token"
+        assert service.credentials.refresh_token is None
+
+    def test_service_lazy_initialization(self):
+        """Test that the API service is not created until accessed"""
+        service = GmailService(access_token="test-access-token")
+        assert service._service is None
+
+    @pytest.mark.asyncio
+    async def test_inject_email_success(self):
+        """Test successful email injection"""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().messages().insert().execute.return_value = {
+            "id": "msg123",
+            "threadId": "thread456",
+            "labelIds": ["INBOX"],
+        }
+        service._service = mock_api
+
+        result = await service.inject_email(
+            raw_email=b"From: test@example.com\r\nSubject: Test\r\n\r\nHello",
+            label_ids=["INBOX"],
+            source_account_name="Test Account",
+        )
+
+        assert result["message_id"] == "msg123"
+        assert result["thread_id"] == "thread456"
+        assert "INBOX" in result["label_ids"]
+
+    @pytest.mark.asyncio
+    async def test_inject_email_default_labels(self):
+        """Test that INBOX is used as default label"""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().messages().insert().execute.return_value = {
+            "id": "msg123",
+            "threadId": "thread456",
+            "labelIds": ["INBOX"],
+        }
+        service._service = mock_api
+
+        # No label_ids specified - should default to INBOX
+        result = await service.inject_email(
+            raw_email=b"From: test@example.com\r\nSubject: Test\r\n\r\nHello",
+        )
+
+        assert result["message_id"] == "msg123"
+
+    @pytest.mark.asyncio
+    async def test_inject_email_api_error(self):
+        """Test that GmailInjectionError is raised on API error"""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().messages().insert().execute.side_effect = Exception("API Error")
+        service._service = mock_api
+
+        with pytest.raises(GmailInjectionError, match="Failed to inject email"):
+            await service.inject_email(
+                raw_email=b"From: test@example.com\r\nSubject: Test\r\n\r\nHello",
+            )
+
+    @pytest.mark.asyncio
+    async def test_verify_access_success(self):
+        """Test successful access verification"""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().getProfile().execute.return_value = {
+            "emailAddress": "test@gmail.com",
+        }
+        service._service = mock_api
+
+        result = await service.verify_access()
+        assert result is True
+
+    @pytest.mark.asyncio
+    async def test_verify_access_failure(self):
+        """Test failed access verification"""
+        service = GmailService(access_token="bad-token")
+
+        mock_api = MagicMock()
+        mock_api.users().getProfile().execute.side_effect = Exception("Invalid token")
+        service._service = mock_api
+
+        result = await service.verify_access()
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_get_email_address_success(self):
+        """Test getting email address"""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().getProfile().execute.return_value = {
+            "emailAddress": "user@gmail.com",
+        }
+        service._service = mock_api
+
+        email = await service.get_email_address()
+        assert email == "user@gmail.com"
+
+    @pytest.mark.asyncio
+    async def test_get_email_address_failure(self):
+        """Test getting email address when API fails"""
+        service = GmailService(access_token="bad-token")
+
+        mock_api = MagicMock()
+        mock_api.users().getProfile().execute.side_effect = Exception("Error")
+        service._service = mock_api
+
+        email = await service.get_email_address()
+        assert email is None