Implements Notion MCP integration core:
- OAuth 2.0 discovery (RFC 9470 + 8414), dynamic client registration,
PKCE token exchange, and refresh with rotation
- NotionMCPAdapter connecting to mcp.notion.com/mcp with fallback
to direct API on known serialization errors
- Response parser translating MCP text responses into dicts matching
NotionHistoryConnector output format
- has_mcp_notion_connector() helper for connector gating
