BackendSrv: include credentials when withCredentials option is set (#23380)

The fetch() API won't send cookies or other type of credentials unless
you set the credentials init option. Some datasources like Prometheus
and Elasticsearch have `withCredentials` option in Browser access mode,
but this option is not currently getting passed in the fetch() API.

Fixes #23338.

public/app/core/utils/fetch.test.ts

@@ -27,16 +27,17 @@ describe('parseUrlFromOptions', () => {
 
 describe('parseInitFromOptions', () => {
   it.each`
-    method       | data           | expected
-    ${undefined} | ${undefined}   | ${{ method: undefined, headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
-    ${'GET'}     | ${undefined}   | ${{ method: 'GET', headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
-    ${'POST'}    | ${{ id: '0' }} | ${{ method: 'POST', headers: { map: { 'content-type': 'application/json', accept: 'application/json, text/plain, */*' } }, body: '{"id":"0"}' }}
-    ${'PUT'}     | ${{ id: '0' }} | ${{ method: 'PUT', headers: { map: { 'content-type': 'application/json', accept: 'application/json, text/plain, */*' } }, body: '{"id":"0"}' }}
-    ${'monkey'}  | ${undefined}   | ${{ method: 'monkey', headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
+    method       | data           | withCredentials | expected
+    ${undefined} | ${undefined}   | ${undefined}    | ${{ method: undefined, headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
+    ${'GET'}     | ${undefined}   | ${undefined}    | ${{ method: 'GET', headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
+    ${'POST'}    | ${{ id: '0' }} | ${undefined}    | ${{ method: 'POST', headers: { map: { 'content-type': 'application/json', accept: 'application/json, text/plain, */*' } }, body: '{"id":"0"}' }}
+    ${'PUT'}     | ${{ id: '0' }} | ${undefined}    | ${{ method: 'PUT', headers: { map: { 'content-type': 'application/json', accept: 'application/json, text/plain, */*' } }, body: '{"id":"0"}' }}
+    ${'monkey'}  | ${undefined}   | ${undefined}    | ${{ method: 'monkey', headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined }}
+    ${'GET'}     | ${undefined}   | ${true}         | ${{ method: 'GET', headers: { map: { accept: 'application/json, text/plain, */*' } }, body: undefined, credentials: 'include' }}
   `(
-    "when called with method: '$method' and data: '$data' then result should be '$expected'",
-    ({ method, data, expected }) => {
-      expect(parseInitFromOptions({ method, data, url: '' })).toEqual(expected);
+    "when called with method: '$method', data: '$data' and withCredentials: '$withCredentials' then result should be '$expected'",
+    ({ method, data, withCredentials, expected }) => {
+      expect(parseInitFromOptions({ method, data, withCredentials, url: '' })).toEqual(expected);
     }
   );
 });

public/app/core/utils/fetch.ts

@@ -7,6 +7,15 @@ export const parseInitFromOptions = (options: BackendSrvRequest): RequestInit =>
   const isAppJson = isContentTypeApplicationJson(headers);
   const body = parseBody(options, isAppJson);
 
+  if (options?.withCredentials) {
+    return {
+      method,
+      headers,
+      body,
+      credentials: 'include',
+    };
+  }
+
   return {
     method,
     headers,