Survey of Manifest-Only Connectors Using Custom Components (Feature Gaps)

Analysis of 5 manifest-only connectors that use custom `components.py` files:

## Connectors Analyzed

**source-gitlab** (certified)
- Custom URL validation with environment-specific logic
- Complex partition routing for hierarchical data relationships
- Code: https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-gitlab/components.py

**source-mailchimp** (certified)
- Runtime HTTP requests for data center extraction: https://github.com/airbytehq/airbyte-python-cdk/issues/713
- Custom record extraction for flattening nested arrays
- Code: https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-mailchimp/components.py

**source-google-sheets** (certified)
- Complex schema parsing and name conversion with configurable sanitization
- Dynamic range-based partitioning for batch processing
- Code: https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-google-sheets/components.py

**source-younium** (community)
- Custom OAuth2 authenticator with environment-specific endpoints
- Token generation with conditional URL selection
- Code: https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-younium/components.py

**source-klaviyo** (certified)
- Custom record transformations with additional API calls
- Sophisticated relationship data merging from API responses
- Custom error handling for DNS resolution issues
- Code: https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-klaviyo/components.py

## Summary
All analyzed connectors implement functionality requiring custom Python logic beyond current YAML dialect capabilities.