Add identifier when authorizing with password

This PR is almost copy of https://github.com/Awesome-Technologies/synapse-admin/pull/601 PR,
authored by @dklimpel

src/synapse/authProvider.test.ts

@@ -30,7 +30,7 @@ describe("authProvider", () => {
 
       expect(ret).toBe(undefined);
       expect(fetch).toBeCalledWith("http://example.com/_matrix/client/r0/login", {
-        body: '{"device_id":null,"initial_device_display_name":"Synapse Admin","type":"m.login.password","user":"@user:example.com","password":"secret"}',
+        body: '{"device_id":null,"initial_device_display_name":"Synapse Admin","type":"m.login.password","identifier":{"type":"m.id.user","user":"@user:example.com"},"password":"secret"}',
         headers: new Headers({
           Accept: "application/json",
           "Content-Type": "application/json",