[BUG]the return value of customized convert should follow Spring secuity standard

[backwind1233]

Describe the bug
by default, a bearer token in request will be convert into an AbstractAuthenticationToken object through spring security framwork, and the AbstractAuthenticationToken object's getName will get subject claim in the bearer token.
but our customized AADB2CJwtBearerTokenAuthenticationConverter’s convert method does not follow the standard, which will cause some unexpected problem.

Exception or Stack Trace

To Reproduce

Code Snippet

 @Override
    public AbstractAuthenticationToken convert(Jwt jwt) {
        OAuth2AccessToken accessToken = new OAuth2AccessToken(
            OAuth2AccessToken.TokenType.BEARER, jwt.getTokenValue(), jwt.getIssuedAt(), jwt.getExpiresAt());
        Collection<GrantedAuthority> authorities = extractAuthorities(jwt);
        AADB2COAuth2AuthenticatedPrincipal principal = new AADB2COAuth2AuthenticatedPrincipal(
            jwt.getHeaders(), jwt.getClaims(), authorities, jwt.getTokenValue());
        return new BearerTokenAuthentication(principal, accessToken, authorities);
    }

Expected behavior

Screenshots

Setup (please complete the following information):

Additional context

Information Checklist

[ZhuXiaoBing-cn]

@backwind1233, You are right. AbstractAuthenticationToken object's getName will get a subject claim in the bearer token for the spring security framework.
But in our AADB2CJwtBearerTokenAuthenticationConverter, Jwt is converted into an implementation class BearerTokenAuthentication of AbstractAuthenticationToken, which has more flexible scalability.
However, an OAuth2AuthenticatedPrincipal object needs to be passed when constructing BearerTokenAuthentication, which will implement the getName method. I think what we need to change is the getName method in OAuth2AuthenticatedPrincipal.

[backwind1233]

@ZhuXiaoBing-cn I suggest don't change the OAuth2AuthenticatedPrincipal's getName method, we can replace BearerTokenAuthentication with our own class

[saragluna]

@backwind1233 @ZhuXiaoBing-cn will this change in #20340 also affect the Prinicipal we're talking in this thread?

[saragluna]

Okay, even though they're all implementing the OAuth2AuthenticatedPrincipal, OAuth2User and DefaultOAuth2AuthenticatedPrincipal. But only the OAuth2User could leverage the usernameAttributeName property. For this reason https://github.com/spring-projects/spring-security/blob/7ef3f619242816683a72b35a1f8b4fb4f32d5203/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/user/OAuth2User.java#L33.