Allow lists in query strings

There are use cases where you may want to add an array of values to a
query string. I.E. `ids[]=1&ids[]=2`.

Previously the `mergeEntries` function was simply replacing any item in
the search params with an identical name. This had the effect of only
including the final entry in the params.

This updates the `mergeEntires` function to just do an append rather
than a replace if the entry name contains `[]`.

__tests__/fetch_request.js

@@ -254,6 +254,14 @@ describe('query params are parsed', () => {
     const urlAndOptionRequest = new FetchRequest("post", "localhost/test", { query: urlSearchParams })
     expect(urlAndOptionRequest.url).toBe("localhost/test?a=1")
   })
+  test('urlSearchParams with list entries', () => {
+    const urlSearchParams = new URLSearchParams()
+    urlSearchParams.append("a[]", 1)
+    urlSearchParams.append("a[]", 2)
+
+    const urlAndOptionRequest = new FetchRequest("post", "localhost/test", {query: urlSearchParams})
+    expect(urlAndOptionRequest.url).toBe("localhost/test?a%5B%5D=1&a%5B%5D=2")
+  });
   test('handles empty query', () => {
     const emptyQueryRequest = new FetchRequest("get", "localhost/test")
     expect(emptyQueryRequest.url).toBe("localhost/test")

src/lib/utils.js

@@ -41,6 +41,7 @@ export function mergeEntries (searchParams, entries) {
     if (value instanceof window.File) continue
 
     if (searchParams.has(name)) {
+    if (searchParams.has(name) && !name.includes('[]')) {
       searchParams.delete(name)
       searchParams.set(name, value)
     } else {