Pass-through client request headers / set X-Forwarded for

[TO-koswald]

Describe the feature

There should be an option similiar to how it's done for the response headers in #44 to pass client request headers to the server.

Use case:

• User-Agent / Client IP (X-FORWARED-FOR header)

Right now our main api receives User-Agent: node and the ip-address of the node server.

Right now to achieve this, we need to create a custom route and proxy them ourselves. We cannot set client: true ,because this would expose an Authorization header that we set.

Additional information

• Would you be willing to help implement this feature?
• Can you think of other implementations of this feature?

Final checks

• Check existing issues.