add: purchased accounts

crates/core/src/config.rs

@@ -192,6 +192,8 @@ pub struct StripeConfig {
     ///
     /// <https://docs.stripe.com/no-code/customer-portal>
     pub billing_portal_url: String,
+    /// The text representation of the price of supporter. (like `$4 USD`)
+    pub supporter_price_text: String,
 }
 
 /// Manuals config (search help, etc)