add device message if quota is exceeding (#2621)

* resultify update_recent_quota()

* add a device-message if quota exceeds QUOTA_WARN_THRESHOLD_PERCENTAGE

* check if a quota warning should be added during housekeeping, this is at least once a day

* dc_get_config("quota_exceeding") is useful for bots

* make clippy happy

* reword QuotaExceedingMsgBody message

* avoid lots of warnings if quota jitters around the warning threshold

* allow clippy::assertions_on_constants

these constants depend on each other, it makes sense to check that they are not changed in an incompatible way

src/config.rs

@@ -156,6 +156,11 @@ pub enum Config {
     #[strum(props(default = "0"))]
     NotifyAboutWrongPw,
 
+    /// If a warning about exceeding quota was shown recently,
+    /// this is the percentage of quota at the time the warning was given.
+    /// Unset, when quota falls below minimal warning threshold again.
+    QuotaExceeding,
+
     /// address to webrtc instance to use for videochats
     WebrtcInstance,