Add ability for Rewrites to overwrite request headers (vercel/turbore…

…po#5139)

### Description

Adds a `request_headers` override to `RewriteVc`, allowing middleware to
modify the request headers for further lookups.

### Testing Instructions

#50567
Re: WEB-1121

crates/turbopack-dev-server/src/source/mod.rs

@@ -531,6 +531,10 @@ pub struct Rewrite {
     /// A [Headers] which will be appended to the eventual, fully resolved
     /// content result. This overwrites any previous matching headers.
     pub response_headers: Option<HeaderListVc>,
+
+    /// A [HeaderList] which will overwrite the values used during the lookup
+    /// process. All headers not present in this list will be deleted.
+    pub request_headers: Option<HeaderListVc>,
 }
 
 pub struct RewriteBuilder {
@@ -544,6 +548,7 @@ impl RewriteBuilder {
                 path_and_query,
                 source: None,
                 response_headers: None,
+                request_headers: None,
             },
         }
     }
@@ -563,6 +568,13 @@ impl RewriteBuilder {
         self
     }
 
+    /// Sets request headers to overwrite the headers used during the lookup
+    /// process.
+    pub fn request_headers(mut self, headers: HeaderListVc) -> Self {
+        self.rewrite.request_headers = Some(headers);
+        self
+    }
+
     pub fn build(self) -> RewriteVc {
         self.rewrite.cell()
     }

crates/turbopack-dev-server/src/source/resolve.rs

@@ -4,7 +4,10 @@ use std::{
 };
 
 use anyhow::{bail, Result};
-use hyper::Uri;
+use hyper::{
+    header::{HeaderName as HyperHeaderName, HeaderValue as HyperHeaderValue},
+    Uri,
+};
 use turbo_tasks::{TransientInstance, Value};
 
 use super::{
@@ -71,6 +74,15 @@ pub async fn resolve_source_request(
                         if let Some(headers) = &rewrite.response_headers {
                             response_header_overwrites.extend(headers.await?.iter().cloned());
                         }
+                        if let Some(headers) = &rewrite.request_headers {
+                            request_overwrites.headers.clear();
+                            for (name, value) in &*headers.await? {
+                                request_overwrites.headers.insert(
+                                    HyperHeaderName::try_from(name)?,
+                                    HyperHeaderValue::try_from(value)?,
+                                );
+                            }
+                        }
                         current_asset_path = new_asset_path;
                         data = ContentSourceData::default();
                     }

crates/turbopack-dev-server/src/source/wrapping_source.rs

@@ -155,6 +155,7 @@ impl GetContentSourceContent for WrappedGetContentSourceContent {
                         .into(),
                     ),
                     response_headers: rewrite.response_headers,
+                    request_headers: rewrite.request_headers,
                 }
                 .cell(),
             )