Release v2.9.0-M1 · akka/akka

What's Changed

chore: MiMa.latestPatchOf for 2.8.4 by @johanandren in #32043
typo in scaladoc Concat$ by @dongxuwang in #32046
clean GraphAssembly related scaladoc since which has gone for a while by @dongxuwang in #32048
fix: DownSelfQuarantinedByRemote should not be triggered by harmless quarantine, #31095 by @patriknw in #32050
doc: Drop usage of scalafiddle by @johanandren in #32052
Fix typo in SourceSpec. by @He-Pin in #32053
feat: Predefined marker interfaces for JSON and CBOR by @johanandren in #32049
chore: remove deprecated-since-2.6.0 Main by @leviramsey in #31933
chore: Drop deprecated cluster client by @johanandren in #32056
update ActorSystemSpec to use property based testing for its name by @dongxuwang in #32045
chore: Drop old TypedActor APIs (after deprecation cycle) by @johanandren in #32057
chore: EventEnvelope with copy methods by @patriknw in #32067
feat: Optionally include serialization binding for ScalaPb by @patriknw in #32070
chore: Drop deprecated typesafe ssl-config usage by @johanandren in #31831
bump: sbt 1.9.4 (was 1.9.3) by @scala-steward in #32075
chore: Migration for dropped AkkaSSLConfig, by @johanandren in #32071
=str Make use of statefulMap to implement zipWithIndex. by @He-Pin in #32061
perf: SerializedEvent optimization by @patriknw in #32068
Replace labels on the image: should be flatMapMerge, but was flatFlattenMerge #28040 by @Captain1653 in #32084

Full Changelog: v2.8.4...v2.9.0-M1