Creating user certificate capable of signing emails (S/MIME) with IdM's CA

Issue

S/MIME stands for Secure/Multipurpose Internet Mail Extension. S/MIME certificates are commonly used as email signing certificates or personal authentication certificates.

In order to create user certificate with ability to sign emails, we need to add S/MIME attributes to usual user certificate. Certificate has to have E-mail Protection extended key usage, provided by exKeyUsageOID 1.3.6.1.5.5.7.3.4.