feat: allow URLSearchParams and string as params in APIRequestContext (follow-up) (#32143)

Follow-up to https://github.com/microsoft/playwright/pull/32120

I made some changes suggested by @yury-s in the previous PR that make a
lot of sense:
- added an example to the documentation
- improved tests
  - check params on the client and server end
  - reverted to non-English characters being used as params

docs/src/api/class-apirequestcontext.md

@@ -369,12 +369,24 @@ context cookies from the response. The method will automatically follow redirect
 Request parameters can be configured with `params` option, they will be serialized into the URL search parameters:
 
 ```js
+// Passing params as object
 await request.get('https://example.com/api/getText', {
   params: {
     'isbn': '1234',
     'page': 23,
   }
 });
+
+// Passing params as URLSearchParams
+const searchParams = new URLSearchParams();
+searchParams.set('isbn', '1234');
+searchParams.append('page', 23);
+searchParams.append('page', 24);
+await request.get('https://example.com/api/getText', { params: searchParams });
+
+// Passing params as string
+const queryString = 'isbn=1234&page=23&page=24';
+await request.get('https://example.com/api/getText', { params: queryString });
 ```
 
 ```java

packages/playwright-core/types/types.d.ts

@@ -16672,12 +16672,24 @@ export interface APIRequestContext {
    * Request parameters can be configured with `params` option, they will be serialized into the URL search parameters:
    *
    * ```js
+   * // Passing params as object
    * await request.get('https://example.com/api/getText', {
    *   params: {
    *     'isbn': '1234',
    *     'page': 23,
    *   }
    * });
+   *
+   * // Passing params as URLSearchParams
+   * const searchParams = new URLSearchParams();
+   * searchParams.set('isbn', '1234');
+   * searchParams.append('page', 23);
+   * searchParams.append('page', 24);
+   * await request.get('https://example.com/api/getText', { params: searchParams });
+   *
+   * // Passing params as string
+   * const queryString = 'isbn=1234&page=23&page=24';
+   * await request.get('https://example.com/api/getText', { params: queryString });
    * ```
    *
    * @param url Target URL.

tests/library/browsercontext-fetch.spec.ts

@@ -123,39 +123,66 @@ it('should add session cookies to request', async ({ context, server }) => {
 
 for (const method of ['fetch', 'delete', 'get', 'head', 'patch', 'post', 'put'] as const) {
   it(`${method} should support params passed as object`, async ({ context, server }) => {
-    const params = {
-      'first-param': 'value2',
-      'second-param': 'value',
-    };
+    const url = new URL(server.EMPTY_PAGE);
+    url.searchParams.set('param1', 'value1');
+    url.searchParams.set('парам2', 'знач2');
 
-    const response = await context.request[method](server.EMPTY_PAGE + '?first-param=value1', { params });
+    const [request, response] = await Promise.all([
+      server.waitForRequest(url.pathname + url.search),
+      context.request[method](server.EMPTY_PAGE, {
+        params: {
+          'param1': 'value1',
+          'парам2': 'знач2',
+        }
+      }),
+    ]);
 
-    const { searchParams } = new URL(response.url());
-    expect(searchParams.getAll('first-param')).toEqual(['value1', 'value2']);
-    expect(searchParams.get('second-param')).toBe('value');
+    const requestParams = new URLSearchParams(request.url.slice(request.url.indexOf('?')));
+    expect(requestParams.get('param1')).toEqual('value1');
+    expect(requestParams.get('парам2')).toBe('знач2');
+
+    const responseParams = new URL(response.url()).searchParams;
+    expect(responseParams.get('param1')).toEqual('value1');
+    expect(responseParams.get('парам2')).toBe('знач2');
   });
 
   it(`${method} should support params passed as URLSearchParams`, async ({ context, server }) => {
-    const params = new URLSearchParams();
-    params.append('first-param', 'value1');
-    params.append('first-param', 'value2');
-    params.append('second-param', 'value');
+    const url = new URL(server.EMPTY_PAGE);
+    const searchParams = new URLSearchParams();
+    searchParams.append('param1', 'value1');
+    searchParams.append('param1', 'value2');
+    searchParams.set('парам2', 'знач2');
 
-    const response = await context.request[method](server.EMPTY_PAGE, { params });
+    const [request, response] = await Promise.all([
+      server.waitForRequest(url.pathname + '?' + searchParams),
+      context.request[method](server.EMPTY_PAGE, { params: searchParams }),
+    ]);
 
-    const { searchParams } = new URL(response.url());
-    expect(searchParams.getAll('first-param')).toEqual(['value1', 'value2']);
-    expect(searchParams.get('second-param')).toBe('value');
+    const requestParams = new URLSearchParams(request.url.slice(request.url.indexOf('?')));
+    expect(requestParams.getAll('param1')).toEqual(['value1', 'value2']);
+    expect(requestParams.get('парам2')).toBe('знач2');
+
+    const responseParams = new URL(response.url()).searchParams;
+    expect(responseParams.getAll('param1')).toEqual(['value1', 'value2']);
+    expect(responseParams.get('парам2')).toBe('знач2');
   });
 
   it(`${method} should support params passed as string`, async ({ context, server }) => {
-    const params = 'first-param=value1&first-param=value2&second-param=value';
+    const url = new URL(server.EMPTY_PAGE);
+    const params = '?param1=value1&param1=value2&парам2=знач2';
 
-    const response = await context.request[method](server.EMPTY_PAGE, { params });
+    const [request, response] = await Promise.all([
+      server.waitForRequest(url.pathname + encodeURI(params)),
+      context.request[method](server.EMPTY_PAGE, { params }),
+    ]);
 
-    const { searchParams } = new URL(response.url());
-    expect(searchParams.getAll('first-param')).toEqual(['value1', 'value2']);
-    expect(searchParams.get('second-param')).toBe('value');
+    const requestParams = new URLSearchParams(request.url.slice(request.url.indexOf('?')));
+    expect(requestParams.getAll('param1')).toEqual(['value1', 'value2']);
+    expect(requestParams.get('парам2')).toBe('знач2');
+
+    const responseParams = new URL(response.url()).searchParams;
+    expect(responseParams.getAll('param1')).toEqual(['value1', 'value2']);
+    expect(responseParams.get('парам2')).toBe('знач2');
   });
 
   it(`${method} should support failOnStatusCode`, async ({ context, server }) => {