SSH allowed_domain templating not documented

[luke-clifton]

For the SSH secrets backend, when creating a role for signing a host key, you can provide a template in the allowed_domains field when you set allowed_users_template = true. The relevant code path is here

This is useful, however, it's also undocumented, which makes me hesitant to use it.

[f4z3r]

@schultz-is just a heads-up that this issue can now be closed as well I think.

[schultz-is]

Excellent, this functionality was documented by #16056. Thanks @f4z3r!