Introduce restate-sharding crate

Part of the effort to decompose the restate-types monolith into focused,
composable utility crates.

Add a new `restate-sharding` crate (in `crates/sharding/`) that defines
the foundational sharding types:

- `KeyRange`: a compact `Copy` newtype over `std::range::RangeInclusive<u64>`.
  16 bytes (vs 24 for std::ops::RangeInclusive), wire-format compatible serde
  and bilrost encoding. Provides iter(), is_overlapping(), and split() helpers.
- `PartitionKey`: type alias for u64
- `WithPartitionKey`: trait for types that carry a partition key

The crate is re-exported from `restate-types::sharding` for ergonomic access.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: AhmedSoliman

Cargo.lock

@@ -83,6 +83,7 @@ restate-service-protocol = { path = "crates/service-protocol" }
 restate-service-protocol-v4 = { path = "crates/service-protocol-v4" }
 restate-storage-api = { path = "crates/storage-api" }
 restate-storage-query-datafusion = { path = "crates/storage-query-datafusion" }
+restate-sharding = { path = "crates/sharding" }
 restate-util-string = { path = "util/string" }
 restate-test-util = { path = "crates/test-util" }
 restate-time-util = { path = "crates/time-util" }

Cargo.toml

@@ -18,4 +18,5 @@ bytestring = { workspace = true }
 
 [dev-dependencies]
 rand = { workspace = true }
+restate-sharding = { workspace = true, features = ["bilrost"] }
 static_assertions = { workspace = true }

crates/encoding/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "restate-sharding"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+publish = false
+
+[features]
+default = []
+serde = ["dep:serde"]
+bilrost = ["dep:bilrost"]
+
+[dependencies]
+restate-workspace-hack = { workspace = true }
+
+bilrost = { workspace = true, optional = true }
+serde = { workspace = true, optional = true }
+
+[dev-dependencies]
+restate-sharding = { path = ".", default-features = false, features = ["serde", "bilrost"] }
+
+flexbuffers = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }