feat(metric-stats): Add cardinality limited outcome id (#3389)

Adds the new outcome id `6` `cardinality_limited` to the outcomes enum.

The outcome will already be emitted for the `METRIC_BUCKET` data
category with this change, but the main purpose is to use the outcome
for metric stats.

CHANGELOG.md

@@ -19,6 +19,7 @@
 - Allow IP addresses in metrics domain tag. ([#3365](https://github.com/getsentry/relay/pull/3365))
 - Support the full unicode character set via UTF-8 encoding for metric tags submitted via the statsd format. Certain restricted characters require escape sequences, see [docs](https://develop.sentry.dev/sdk/metrics/#normalization) for the precise rules. ([#3358](https://github.com/getsentry/relay/pull/3358))
 - Stop extracting count_per_segment and count_per_op metrics. ([#3380](https://github.com/getsentry/relay/pull/3380))
+- Add `cardinality_limited` outcome with id `6`. ([#3389](https://github.com/getsentry/relay/pull/3389))
 - Extract `cache.item_size` and `cache.hit` metrics. ([#3371]https://github.com/getsentry/relay/pull/3371)
 
 **Internal**:

relay-server/src/services/outcome.rs

@@ -80,6 +80,7 @@ impl OutcomeId {
     const INVALID: OutcomeId = OutcomeId(3);
     const ABUSE: OutcomeId = OutcomeId(4);
     const CLIENT_DISCARD: OutcomeId = OutcomeId(5);
+    const CARDINALITY_LIMITED: OutcomeId = OutcomeId(6);
 
     pub fn as_u8(self) -> u8 {
         self.0
@@ -102,6 +103,7 @@ trait TrackOutcomeLike {
             OutcomeId::INVALID => "invalid",
             OutcomeId::ABUSE => "abuse",
             OutcomeId::CLIENT_DISCARD => "client_discard",
+            OutcomeId::CARDINALITY_LIMITED => "cardinality_limited",
             _ => "<unknown>",
         }
     }
@@ -188,7 +190,7 @@ impl Outcome {
             Outcome::Filtered(_) | Outcome::FilteredSampling(_) => OutcomeId::FILTERED,
             Outcome::RateLimited(_) => OutcomeId::RATE_LIMITED,
             #[cfg(feature = "processing")]
-            Outcome::CardinalityLimited => OutcomeId::RATE_LIMITED,
+            Outcome::CardinalityLimited => OutcomeId::CARDINALITY_LIMITED,
             Outcome::Invalid(_) => OutcomeId::INVALID,
             Outcome::Abuse => OutcomeId::ABUSE,
             Outcome::ClientDiscard(_) => OutcomeId::CLIENT_DISCARD,
@@ -197,17 +199,16 @@ impl Outcome {
     }
 
     /// Returns the `reason` code field of this outcome.
-    pub fn to_reason(&self) -> Option<Cow<str>> {
+    pub fn to_reason(&self) -> Option<Cow<'_, str>> {
         match self {
             Outcome::Invalid(discard_reason) => Some(Cow::Borrowed(discard_reason.name())),
             Outcome::Filtered(filter_key) => Some(filter_key.clone().name()),
             Outcome::FilteredSampling(rule_ids) => Some(Cow::Owned(format!("Sampled:{rule_ids}"))),
-            //TODO can we do better ? (not re copying the string )
-            Outcome::RateLimited(code_opt) => code_opt
-                .as_ref()
-                .map(|code| Cow::Owned(code.as_str().into())),
+            Outcome::RateLimited(code_opt) => {
+                code_opt.as_ref().map(|code| Cow::Borrowed(code.as_str()))
+            }
             #[cfg(feature = "processing")]
-            Outcome::CardinalityLimited => Some(Cow::Borrowed("cardinality_limited")),
+            Outcome::CardinalityLimited => None,
             Outcome::ClientDiscard(ref discard_reason) => Some(Cow::Borrowed(discard_reason)),
             Outcome::Abuse => None,
             Outcome::Accepted => None,