Support removal of special charaters in property mapping

**Is your feature request related to a problem? Please describe.**
I use authentik to manage directory of polish users with some special accented characters like `ąęół`. When users log in to external system using authentik as OIDC provider, 3rd party system is replacing any special character with a `-`. For example, name like `Łukasz Sokół` would end up being `-ukasz-sok--` which is quite bad.

**Describe the solution you'd like**
I would like to run python's `unidecode` function on username before sending it to that specific 3rd party service.

**Describe alternatives you've considered**
The alternative wouyld be asking 3rd party to correctly handle accented letters.

**Additional context**
None that I'm aware of being relevant.