Header propagation

[robinevers93]

Hello!

I'm writing an MCP server which has a requirement to do an auth check on each tool call.
The recommended way to implement this is by letting the MCP client handle obtaining the token, and passing the token from the MCP client to the MCP server through the header.

I have implemented a proposed solution to provide support in chimp for this. There are two main changes in my suggestion:

1. The mcpEndpoint method takes an optional name of the header (defaulted to no header).
2. A handleWithHeader method is added in which the logic takes in the value of the header as a parameter.

I included unit tests for my changed and added an example on how it can be used.

I also recorded a video to show it working, I'll attach it to the PR.

chimp-with-header-propagation.mov

Thanks a lot for considering this PR!

[adamw]

Thanks! I wonder if there might be situations, where multiple headers might be needed? Then, maybe we could simply pass a Seq[Header] (obtained via extractFromRequest(_.headers))?

Also, some of the in-code comments have been removed, is that on purpose?

Finally, at least a short mention in the readme would be great :)

[robinevers93]

Great points, I shall make those changes and push them up, thank you!

[robinevers93]

Okay, I have made those changes. Since we're using the Header type rather than the String type now, it became unnecessary to pass in a list of header names to def mcpEndpoint, as the tool logic can filter on the name if this is required.

Attaching a new video which shows the logic working using this approach.

updated-chimp-header-handling.mov

[adamw]

Awesome, thanks! :)