Whitelist IP checks

[r0wdy1]

1. Add a predefined env variable for whitelist invite code (32 bytes random bytes as hex)
2. When processing a request from /transactions endpoint check X-Auth-WL header. Compare the value with whitelist invite code
   1. if equal bypass geo IP checks
   2. else continue as usual
3. Add a service to check invite code at endpoint GET /wl/${wlInviteCode}, which returns 200 if wlInviteCode == env.whiteListInviteCode else 404