allow to change from schnupperant to scheckbuch

src/model/user/scheckbuch.rs

@@ -189,27 +189,26 @@ impl ScheckbuchUser {
     }
 
     // TODO: make private
-    pub(crate) async fn notify(
-        &self,
-        db: &SqlitePool,
-        mail: &str,
-        smtp_pw: &str,
-    ) -> Result<(), String> {
-        self.send_welcome_mail_to_user(db, mail, smtp_pw).await?;
+    pub(crate) async fn notify(&self, db: &SqlitePool, smtp_pw: &str) -> Result<(), String> {
         self.notify_coxes_about_new_scheckbuch(db).await;
+        self.send_welcome_mail_to_user(db, smtp_pw).await?;
 
         Ok(())
     }
 
-    async fn send_welcome_mail_to_user(
+    pub(crate) async fn send_welcome_mail_to_user(
         &self,
         db: &SqlitePool,
-        mail: &str,
         smtp_pw: &str,
     ) -> Result<(), String> {
+        let Some(mail) = &self.mail else {
+            return Err(
+                "Kann Mail nicht versenden, weil der User keine Mailadresse hinterlegt hat.".into(),
+            );
+        };
         Mail::send_single(
             db,
-            mail,
+            &mail,
             "ASKÖ Ruderverein Donau Linz | Dein Scheckbuch wartet auf Dich",
             format!(
 "Hallo {0},