[FEATURE] Enable configuration of variable used for display name, prevent PII exposure.

[WirtsLegs]

Is your feature request related to a problem? Please describe.
Currently the app uses a user's email for showing ownership of snippets etc, this should be configurable to for example use preferredUsername etc. This is especially important given the PII that tends to be in people's email and is now plastered on public snippets

Describe the solution you'd like
Addition of the ability to change what is used for a user's display name with a environment variable, and the default should change to username or preferredUsername for privacy reasons

Describe alternatives you've considered
Not any other good solutions for some environment types

Additional context
No additional context