Azure AD B2C tight integration with SWA (or fixing the preview env redirect link for aad in the cli)

**Is your feature request related to a problem? Please describe.**
Most people building SaaS apps on SWA and Azure need user login, the login provider that makes sense is b2c (equivalent of cognito).

Problem is: b2c have to be configured manually, with one redirect link (or more, but it's manual), one tenant (can't mix prod and preview) ...

and the real problem arises when you're in a preview env and you want to authenticate a user.
It's not a good practice to create a redirect link on b2c for every preview env.

**Describe the solution you'd like**
Like Storage, Functions and APIs, CI/CD, environments... SWA should include a good auth provider like B2C pre-packaged into the app.

> or maybe find a solution for the mess of integrating B2C with SWA

**Describe alternatives you've considered**
Tried using the default AAD IDP... yet, doesn't cover the common use case of a "public-facing saas platform".


as you see in the pic above, once the preview env got provisioned, I went to aad and added the redirect link manually.
an easy fast fix, is including this in the tooling, a better fix, is integrating b2c, that's my opinion.