Validate identity names

[IronCore864]

Currently, the identity name is a string, and when validating an identity, we don't set any limit on what can be used as the name. When adding identities, they are directly read from the YAML without validation either. So, technically, users can now use anything as part of their identity name.

We want to add some validation on the name, for example, ^a-zA-Z0-9_\-, so that it doesn't contain weird characters.