Allow to override the local authentication mock

**Is your feature request related to a problem? Please describe.**
In local development I would like to test against an existing Azure AD B2C tenant created specifically for this purpose

**Describe the solution you'd like**
I would like a simple swa start --argument / configuration setting to override the default local authentication mock

**Describe alternatives you've considered**
I am not aware of any alternatives, but this might be possible already

**Additional context**
[Azure AD B2C operations best practice (first row)](https://learn.microsoft.com/en-us/azure/active-directory-b2c/best-practices#operations)