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/invites.js

+import request from '@/utils/request'
+import { getToken } from '@/utils/auth'
+import { baseName } from './utils'
+
+export async function generateInviteToken(max_use, expires_at, authHost, token) {
+  return await request({
+    baseURL: baseName(authHost),
+    url: `/api/pleroma/admin/users/invite_token`,
+    method: 'post',
+    headers: authHeaders(token),
+    data: expires_at && expires_at.length > 0 ? { max_use, expires_at } : { max_use }
+  })
+}
+
+export async function listInviteTokens(authHost, token) {
+  return await request({
+    baseURL: baseName(authHost),
+    url: `/api/pleroma/admin/users/invites`,
+    method: 'get',
+    headers: authHeaders(token)
+  })
+}
+
+const authHeaders = (token) => token ? { 'Authorization': `Bearer ${getToken()}` } : {}