templates: Add dummy RemoteAddr to httpInclude request, proxy compatibility

[ThanmayNath]

Issue:
This pull request addresses fixes #5835, which was created to track the progress of the discussion on the Caddy community forum: https://caddy.community/t/file-server-httpinclude-with-x-forwarded-for/21087. The issue discusses the need to allow the virtual request of httpInclude of a file_server to include the X-Forwarded-For header. Currently, the X-Forwarded-For header is not set in the virtual request, which poses a challenge for applications that rely on this header to determine the client's IP address and make decisions based on it.

Goal:
The goal of this enhancement is to modify the funcHTTPInclude function in the Caddy codebase to include the X-Forwarded-For header in the virtual request. This change will enable reverse proxies to set the X-Forwarded-For header, ensuring that the client's IP address is correctly provided to the target endpoint. This modification is essential for applications that depend on the X-Forwarded-For header for various functionalities, such as authentication, logging, or content customization.

Proposed Changes:

• In the funcHTTPInclude function, we will create a new virtual request (virtReq).
• We will set the Host header of the virtual request to match the original request's Host.
• The X-Forwarded-For header will be added to the virtual request, including the client's IP address obtained from the c.RemoteIP() function.
• Other headers, such as Accept-Encoding, will be set as needed.
• The virtual request will be performed as before, ensuring that the target endpoint receives the X-Forwarded-For header.

[CLAassistant]

All committers have signed the CLA.

[francislavoie]

This isn't the right change. We don't want to touch X-Forwarded-For at all here. All we need to do is set virtReq.RemoteAddr = "127.0.0.1" or something to that effect.

[ThanmayNath]

@francislavoie Thank you for your prompt feedback and guidance. I've made the suggested changes to the code as you recommended. I added the line to set virtReq.RemoteAddr = "127.0.0.1" as you mentioned. This should ensure that the RemoteAddr is correctly configured for virtual requests.

Once again, thank you for your assistance in reviewing this code.

[ThanmayNath]

Hi @francislavoie,

I've looked into the requested changes, but it appears that I'm unable to view the specific modifications in the code.
The message I'm getting is: "We went looking everywhere, but couldn’t find those commits. Sometimes commits can disappear after a force-push."

I want to ensure that I address your feedback correctly, so I would appreciate it if you could provide some additional details or clarification regarding the changes you'd like to see. This will help me make the necessary adjustments promptly.

Thank you for your patience and assistance in resolving this.

[francislavoie]

I've already applied those changes. Check the commits.

[ThanmayNath]

@francislavoie I apologize for any confusion. I'll re-check the commits to make sure I didn't miss anything. If you have any specific files or lines of code that you'd like me to focus on, please let me know.

[francislavoie]

There's nothing left to do. Just getting confirmation that it fixes the issue from the person who reported it.