Derive macros for better-auth entity traits.

Provides #[derive(AuthUser)], #[derive(AuthSession)], etc. to auto-implement the entity traits from better_auth_core::entity for custom struct types.

Example

use better_auth_derive::AuthUser;

#[derive(Clone, Debug, Serialize, AuthUser)]
pub struct MyUser {
    pub id: String,
    pub email: Option<String>,
    #[auth(field = "name")]
    pub display_name: Option<String>,
    pub email_verified: bool,
    pub image: Option<String>,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
    pub username: Option<String>,
    pub display_username: Option<String>,
    pub two_factor_enabled: bool,
    pub role: Option<String>,
    pub banned: bool,
    pub ban_reason: Option<String>,
    pub ban_expires: Option<DateTime<Utc>>,
    pub metadata: HashMap<String, serde_json::Value>,
}