bugfix/feat:Allow other LDAP field besides "mail" to map to email adress, or fallback to made up email

[Mxbonn]

Summary

if the userinfo of LDAP does not return a mail field, librechat will not authenticate even if ldap authenticated succesfully.

Change Type

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• [x] Bug fix (non-breaking change which fixes an issue)

Testing

Please describe your test process and include instructions so that we can reproduce your test. If there are any important variables for your testing configuration, list them here.

Test Configuration:

Checklist

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• [x] My code adheres to this project's style guidelines
• [x] I have performed a self-review of my own code
• [ ] I have made pertinent documentation changes ->
  • I could not seem to find the source to update https://www.librechat.ai/docs/configuration/authentication/ldap
• [x] My changes do not introduce new warnings
• [ ] A pull request for updating the documentation has been submitted.
  • could you point me to the correct git repo for this?