Feature request: Discover workflow actions from MCP servers

Scope & Context Twenty's workflow engine supports a fixed set of built-in action types (Send Email, HTTP Request, Code, etc.). When users want to integrate external services into their workflows, there's no plugin mechanism — each new integration requires custom action types hardcoded into the server and frontend. The [Model Context Protocol (MCP)]( is an open standard that already solves tool discovery (tools/list with JSON Schema) and tool execution (tools/call with structured output) over HTTP. This ticket proposes adding native MCP server support so that any MCP-compatible service can be registered and its tools automatically appear as workflow actions — no code changes to Twenty required. This covers the workflow engine, workflow builder UI, a new Settings page for managing MCP server connections, and a tiered authentication model including OAuth 2.1 for MCP servers that require user consent flows. Current behavior Users can only use the built-in workflow actio…