feat(txname): Apply transaction rules to legacy SDKs (#2250)

getsentry/sentry#51437 expanded the scope of
transaction name clustering to transactions from old SDKs that do not
send a `source` annotation yet. This PR enables the application of rules
to this type of transactions in Relay.

Because there is a potential of triggering the cardinality limiter, I
gated this new behavior with a feature flag.

The condition for applying clusterer rules has now become more
complicated, so I decided to remove / ignore the `scope` configuration
flag entirely.

Author: jjbayer

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Add filter based on transaction names. ([#2118](https://github.com/getsentry/relay/pull/2118))
 - Drop profiles without a transaction in the same envelope. ([#2169](https://github.com/getsentry/relay/pull/2169))
 - Use GeoIP lookup also in non-processing Relays. Lookup from now on will be also run in light normalization. ([#2229](https://github.com/getsentry/relay/pull/2229))
+- Scrub identifiers from transactions for old SDKs. ([#2250](https://github.com/getsentry/relay/pull/2250))
 
 ## 23.6.1
 

relay-dynamic-config/src/feature.rs

@@ -15,6 +15,8 @@ pub enum Feature {
     DeviceClassSynthesis,
     /// Enables metric extraction from spans.
     SpanMetricsExtraction,
+    /// Apply transaction normalization rules to transactions from legacy SDKs.
+    NormalizeLegacyTransactions,
     /// Forward compatibility.
     Unknown(String),
 }
@@ -49,6 +51,9 @@ impl Serialize for Feature {
             }
             Feature::DeviceClassSynthesis => "organizations:device-class-synthesis",
             Feature::SpanMetricsExtraction => "projects:span-metrics-extraction",
+            Feature::NormalizeLegacyTransactions => {
+                "organizations:transaction-name-normalize-legacy"
+            }
             Feature::Unknown(s) => s,
         })
     }