Reusable Custom API Key Connections

Problem:
Currently, when we need to call external APIs within AgenticFlow, we often have to configure the API Call node (with headers, base URL, authentication methods, etc.) from scratch each time, or duplicate existing nodes. This process is repetitive, error-prone, and can lead to messy workflows, especially when the same API is used across multiple workflows or by multiple agents. If an API key or a common header needs updating, we have to find and update it in many places.

Proposed Solution:
I propose the ability to create and save "Custom API Key Connections" or "Reusable API Call Nodes." This would allow us to:

1. Configure Once: Define a custom API connection with its base URL, authentication method (e.g., API key in header, Bearer token), common headers, and even common base parameters.

2. Save & Reuse: Save this configuration as a reusable component/node that can be easily selected and used in any workflow or by any agent, similar to how we select built-in MCPs or other nodes.

3. Centralized Updates: If the API key, a header, or a base parameter needs to be updated, we could change it in one central place (the saved custom API connection), and this update would automatically apply to all instances where that connection is used.

Related Feature Request:
This would also synergize incredibly well with the existing request for "Reusable Custom API Call Nodes for Effortless Workflow" (https://agenticflow.featurebase.app/p/reusable-custom-api-call-nodes-for-effortless-workflow), as that focuses on reusing the entire call structure, while this request emphasizes reusable connection/authentication configurations that could underpin those custom call nodes.