feat(http): keep slashes in queryParams in redirects (#4928)

* refactor(http): extract logic into constructRedirectPath

This allows us to easily test our redirect path construction logic where we get
the relative path, the query string and construct a redirect path.

By extracting this from `redirect`, we can easily test this logic in a unit
test.

I did this so we could test some logic where slashes in query strings should be
made human-friendly for users.

* feat(testing): add tests for constructRedirectPath

Co-authored-by: Asher <ash@coder.com>

test/unit/node/http.test.ts

@@ -1,4 +1,5 @@
-import { relativeRoot } from "../../../src/node/http"
+import { getMockReq } from "@jest-mock/express"
+import { constructRedirectPath, relativeRoot } from "../../../src/node/http"
 
 describe("http", () => {
   it("should construct a relative path to the root", () => {
@@ -9,3 +10,46 @@ describe("http", () => {
     expect(relativeRoot("/foo/bar/")).toStrictEqual("./../..")
   })
 })
+
+describe("constructRedirectPath", () => {
+  it("should preserve slashes in queryString so they are human-readable", () => {
+    const mockReq = getMockReq({
+      originalUrl: "localhost:8080",
+    })
+    const mockQueryParams = { folder: "/Users/jp/dev/coder" }
+    const mockTo = ""
+    const actual = constructRedirectPath(mockReq, mockQueryParams, mockTo)
+    const expected = "./?folder=/Users/jp/dev/coder"
+    expect(actual).toBe(expected)
+  })
+  it("should use an empty string if no query params", () => {
+    const mockReq = getMockReq({
+      originalUrl: "localhost:8080",
+    })
+    const mockQueryParams = {}
+    const mockTo = ""
+    const actual = constructRedirectPath(mockReq, mockQueryParams, mockTo)
+    const expected = "./"
+    expect(actual).toBe(expected)
+  })
+  it("should append the 'to' path relative to the originalUrl", () => {
+    const mockReq = getMockReq({
+      originalUrl: "localhost:8080",
+    })
+    const mockQueryParams = {}
+    const mockTo = "vscode"
+    const actual = constructRedirectPath(mockReq, mockQueryParams, mockTo)
+    const expected = "./vscode"
+    expect(actual).toBe(expected)
+  })
+  it("should append append queryParams after 'to' path", () => {
+    const mockReq = getMockReq({
+      originalUrl: "localhost:8080",
+    })
+    const mockQueryParams = { folder: "/Users/jp/dev/coder" }
+    const mockTo = "vscode"
+    const actual = constructRedirectPath(mockReq, mockQueryParams, mockTo)
+    const expected = "./vscode?folder=/Users/jp/dev/coder"
+    expect(actual).toBe(expected)
+  })
+})