Is your feature request related to a problem? Please describe.
In Auth TODO indicates missing standard JWT fields, and i think we can implement JWT Claims using field that stated in Here

Describe the solution you'd like
Add new fields to the existing TokenInfo struct using pointer types for optional values
maybe something like this

type TokenInfo struct {
    // Existing fields (unchanged)
    Scopes     []string
    Expiration time.Time
    Extra      map[string]any
    
    // New standard JWT fields
    Subject   *string    `json:"sub,omitempty"`   // Subject (user identifier)
    Issuer    *string    `json:"iss,omitempty"`   // Issuer (who issued the token)
    Audience  []string   `json:"aud,omitempty"`   // Audience (intended recipients)
    IssuedAt  *time.Time `json:"iat,omitempty"`   // Issued at time
    NotBefore *time.Time `json:"nbf,omitempty"`   // Not valid before time
    JWTID     *string    `json:"jti,omitempty"`   // JWT ID (unique identifier)
}

Still thinking the access pattern, might be something like below

tokenInfo := auth.TokenInfoFromContext(ctx)
if tokenInfo != nil {
    // Safe access with nil checks
    if tokenInfo.Subject != nil {
        userID := *tokenInfo.Subject
    }
    
    // Audience is a slice, can be checked for length
    if len(tokenInfo.Audience) > 0 {
        primaryAudience := tokenInfo.Audience[0]
    }
    
    // Time fields with nil checks
    if tokenInfo.IssuedAt != nil {
        issuedTime := *tokenInfo.IssuedAt
    }
}

Describe alternatives you've considered

1. Using the existing Extra map
   Store JWT claims in TokenInfo.Extra as map[string]any
   Pros: No struct changes needed
   Cons: No type safety, requires type assertions, error-prone
2. Create a separate JWTTokenInfo struct
   New struct that embeds TokenInfo with JWT fields
   Pros: Clean separation, no existing struct changes
   Cons: Breaking change, requires new context functions, fragments the API
3. Add JWT claims as methods instead of fields
   Functions like GetSubject(), GetIssuer() that parse from Extra
   Pros: Backward compatible, encapsulated logic
   Cons: Performance overhead, still requires Extra map usage
   NB: Will taking https://github.com/golang-jwt/jwt/blob/main/claims.go#L13 as reference during development

Additional context
NA