fix(api): send correct staff emails and allow suppressing them (#3048)

fluxer_admin/src/utils/forms.rs

@@ -100,6 +100,10 @@ impl MultiValueForm {
         })
     }
 
+    pub fn opt_out_value(&self, key: &str) -> bool {
+        !self.contains_key(&format!("{key}_present")) || self.bool_value(key)
+    }
+
     pub fn list_values(&self, key: &str) -> Vec<String> {
         self.fields
             .get(key)