Fix test suite for Node.js 19.1

The header setters are now no-op functions since Node.js 19.1. Nock, the
http mocking library we use for our transmitter tests uses these
setters so our tests break. This commit uses the `rawHeaders` attribute
instead to get green tests until the issue is fixed in either side.

More info: nodejs/node#45510

src/__tests__/transmitter.test.ts

@@ -267,7 +267,8 @@ describe("Transmitter", () => {
       nock("http://example.invalid")
         .get("/301")
         .reply(301, undefined, {
-          Location: "http://example.invalid/302"
+          Location: "http://example.invalid/302",
+          FooHeader: "Location"
         })
         .get("/302")
         .reply(302, undefined, {

src/transmitter.ts

@@ -137,7 +137,7 @@ export class Transmitter {
     return stream => {
       const responseStatus = stream.statusCode ?? 999
       const isRedirect = REDIRECT_STATUS_CODES.indexOf(responseStatus) !== -1
-      const newURL = stream.headers?.location
+      const newURL = this.getLocationHeader(stream.rawHeaders || [])
 
       if (isRedirect && typeof newURL !== "undefined") {
         const redirectCount = callback[REDIRECT_COUNT] ?? 0
@@ -169,6 +169,22 @@ export class Transmitter {
     }
   }
 
+  // Temporary fix to deal with the header setter removal in Node.js 19
+  // https://github.com/nodejs/node/issues/45510
+  private getLocationHeader(rawHeaders: Array<any>): string | undefined {
+    let location
+    rawHeaders.forEach((element, index) => {
+      // Skip odd indices as rawHeaders are represented as an array of pairs (key, value)
+      if (Math.abs(index % 2) == 1) return
+
+      if (element == "Location") {
+        location = rawHeaders[index + 1]
+      }
+    })
+
+    return location
+  }
+
   private configParams(): URLSearchParams {
     const config_data = this.#config.data