Generate invite tokens from admin-fe

This MR allows to create invite tokens, list them on a separate tab, invite users via email. It also updates error handling and allows to generate tokens for resetting password.

Closes #28 (closed)

src/api/__mocks__/users.js

@@ -30,7 +30,7 @@ export async function fetchUsers(filters, authHost, token, page = 1) {
 }
 
 export async function getPasswordResetToken(nickname, authHost, token) {
-  return Promise.resolve({ data: 'g05lxnBJQnL' })
+  return Promise.resolve({ data: { token: 'g05lxnBJQnL', link: 'http://url/api/pleroma/password_reset/g05lxnBJQnL' }})
 }
 
 export async function toggleUserActivation(nickname, authHost, token) {