feat(admin): add user role dialog

Admins change a user's role and see the change log. The last admin
gets a clear error when deleting their own account.

src/utils/admin.test.js

@@ -1,7 +1,7 @@
 // @vitest-environment jsdom
 import {describe, expect, it} from 'vitest';
 import {refreshSession} from './api.js';
-import {viewAs} from './admin.js';
+import {changeUserRole, fetchRoleChanges, viewAs} from './admin.js';
 import {fetchRoutes, json} from '../test/fetchRoutes.js';
 
 describe('viewAs', () => {
@@ -25,3 +25,27 @@ describe('viewAs', () => {
         await switching;
     });
 });
+
+describe('role changes', () => {
+    it('changeUserRole puts the new and the expected role', async () => {
+        fetchRoutes({'PUT /api/admin/users/7/role': json(204)});
+
+        await changeUserRole(7, 'AUDITOR', 'USER');
+
+        const [url, init] = fetch.mock.calls[0];
+        expect(url).toMatch(/\/api\/admin\/users\/7\/role$/);
+        expect(init.method).toBe('PUT');
+        expect(JSON.parse(init.body)).toEqual({role: 'AUDITOR', expectedRole: 'USER'});
+    });
+
+    it('fetchRoleChanges gets the log of the user', async () => {
+        fetchRoutes({'GET /api/admin/users/7/role-changes': json(200, {results: []})});
+        const signal = new AbortController().signal;
+
+        await fetchRoleChanges(7, {signal});
+
+        const [url, init] = fetch.mock.calls[0];
+        expect(url).toMatch(/\/api\/admin\/users\/7\/role-changes$/);
+        expect(init.signal).toBe(signal);
+    });
+});