Additional information for someone who tries to achieve the same as I.
The invite of the users can fail with the following message:

Try to invite user: 
Error inviting users from ldap. Count 0: Failed to invite user 

Caused by:
    0: http error making request reqwest::Error { kind: Status(500), url: Url { scheme: "http", cannot_be_a_base: false, username: "", password: None, host: Some(Domain("vaultwarden")), port: None, path: "/admin/invite", query: None, fragment: None } }
    1: HTTP status server error (500 Internal Server Error) for url (http:https://vaultwarden/admin/invite)

This is caused because authentik has users for the outposts as service accounts. Those are sent if a search query from vaultwarden_ldap is done. This service users hve an empty mail field. So the vaultwarden_ldap fails to send new invites, because the mail is empty. I fixed this by editing the search_filter to check for empt mails: ldap_search_filter = "(&(objectClass=user)(mail=*@*))".
This works now.

@ViViDboarder To prevent this error and crash of the whole program, could you add a check if the mail is empty in the function invite_from_ldap to simply go further and log it.

Originally posted by @Rufmord in #99 (comment)