[FEATURE REQ] Investigate whether we can deprecate azure-spring-boot-starter-active-directory-b2c.

[chenrujun]

Investigate whether we can deprecate azure-spring-boot-starter-active-directory-b2c.

1, List all AAD B2C's features that spring-security can not provide.
2. Investigate if we can add these features in spring-security-repo.

[zhichengliu12581]

Currently, our azure-spring-boot-starter-active-directory-b2c provides the following functions:
As webApp:

1. We will help users choose the client to log in, logout and reset password etc.
2. We can redirect user to correct page when user logout.
3. We support user forgot password on login page.

As webapi:

1. We help users provide trusted accessTokens from multiple issuers (according to the information provided by users)
2. We helped users to add verification of the audience in the accessToken
3. Verification of the issuer in the accessToken obtained by the user (this is the same function as in the first point)

Common functions:
1.Help users configure the client (including authentication_type and client_credentials types).
2. We can obtain the information in scope and role at the same time for permission control (Deprecated and instead by AADJwtBearerTokenAuthenticationConverter), and spring security support custom permission.

When we use spring Security directly, the functions we have been able to provide are:

• When used as a webapi:
  1. Spring Security can support multi Tenant, similar to the sample provided by spring:
  2. In the provision of multi Tenant, users can customize the verification of audience.
• When used as a webapp:
  1. Users can determine the default client through spring configuration
  2. We can add logout uri and redirect user to correct page with spring security.
  3. B2C support reset password in login page now.
• When using common fucntions:
  1. Users can configure the information of each client by themselves

Summary:
We can Deprecated azure-spring-boot-starter-active-directory-b2c, because all functions are already supported by springSecurity, and users can also configure some of them by themselves.