feat: Donation request device message (#6913)

A donation request device message is added if >= 100 messages have been sent and delivered. The
condition is checked every 30 days since the first message is sent. The message is added only once.

src/context.rs

@@ -1054,6 +1054,12 @@ impl Context {
                 .await?
                 .to_string(),
         );
+        res.insert(
+            "donation_request_next_check",
+            self.get_config_i64(Config::DonationRequestNextCheck)
+                .await?
+                .to_string(),
+        );
         res.insert(
             "first_key_contacts_msg_id",
             self.sql