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

@@ -29,6 +29,10 @@ export async function fetchUsers(filters, authHost, token, page = 1) {
   }})
 }
 
+export async function getPasswordResetToken(nickname, authHost, token) {
+  return Promise.resolve({ data: 'g05lxnBJQnL' })
+}
+
 export async function toggleUserActivation(nickname, authHost, token) {
   const response = users.find(user => user.nickname === nickname)
   return Promise.resolve({ data: { ...response, deactivated: !response.deactivated }})