Split out policy file (de)serialization to a subcrate

Cargo.toml

@@ -1,6 +1,14 @@
 [workspace]
 resolver = "3"
-members = [".", "crates/api", "crates/cfg", "crates/cli", "crates/zonedata"]
+members = [
+    ".",
+    "crates/cli",
+
+    "crates/api",
+    "crates/cfg",
+    "crates/policy-file",
+    "crates/zonedata",
+]
 default-members = [".", "crates/cli"]
 
 [workspace.package]
@@ -91,6 +99,9 @@ version = "0.2.15"
 [workspace.dependencies.serde]
 version = "1.0"
 
+[workspace.dependencies.serde_with]
+version = "3"
+
 # 'toml' is a Serde-compatible library for working with TOML documents.
 #
 # It is used throughout the Rust ecosystem and is maintained accordingly.
@@ -119,9 +130,10 @@ daemonbase         = { version = "0.1.5", features = ["tokio"] }
 serde              = { workspace = true, features = ["derive", "rc"] }
 rayon = "1.10.0"
 serde_json         = "1.0"
-serde_with         = "3"
 url                = { version = "2.4", features = ["serde"] }
 
+serde_with.workspace = true
+
 # `futures` provides some async functionality not available in `std` yet. It's
 # quite a big crate, and we only need a subset of the functionality, so we only
 # import the `-util` subcrate.
@@ -183,6 +195,7 @@ idna_adapter = { version = "=1.0.0" }
 
 cascade-api = { path = "crates/api" }
 cascade-cfg = { path = "crates/cfg" }
+cascade-policy-file = { path = "crates/policy-file" }
 cascade-zonedata = { path = "crates/zonedata" }
 
 # 'clap' is used for top-level configuration of the command-line interface (most

crates/cli/Cargo.toml

@@ -39,6 +39,7 @@ path = "../api"
 # The CLI delegates to Clap to handle basic concerns like argument parsing.
 [dependencies.clap]
 workspace = true
+default-features = true
 features = ["cargo", "derive", "env", "wrap_help"]
 
 # The CLI uses 'jiff' to process timestamps and durations, and to print them in

crates/policy-file/Cargo.toml

@@ -0,0 +1,50 @@
+[package]
+name = "cascade-policy-file"
+description = "Cascade's policy files."
+
+authors.workspace = true
+homepage.workspace = true
+documentation.workspace = true
+repository.workspace = true
+license.workspace = true
+
+version.workspace = true
+rust-version.workspace = true
+edition.workspace = true
+
+readme = "README.md"
+
+
+# --- Dependencies -------------------------------------------------------------
+
+[dependencies]
+
+# The user can specify filesystem paths to Cascade. Paths need to be represented
+# in a platform-independent way, ruling out 'std::path::Path'. 'camino' offers
+# UTF-8-only paths that match this requirement.
+[dependencies.camino]
+workspace = true
+features = ["serde1"]
+
+[dependencies.domain]
+workspace = true
+features = ["tsig", "serde"]
+
+# 'foldhash' offers fast, non-cryptographic hash tables.
+[dependencies.foldhash]
+workspace = true
+
+# 'jiff' is a general-purpose time library.
+[dependencies.jiff]
+workspace = true
+
+# 'serde' and 'toml' are used for parsing TOML configuration files.
+[dependencies.serde]
+workspace = true
+features = ["derive"]
+[dependencies.toml]
+workspace = true
+
+# 'serde-with' provides helpers for 'serde'.
+[dependencies.serde_with]
+workspace = true

crates/policy-file/src/lib.rs

@@ -0,0 +1,32 @@
+//! Definitions for Cascade policy files.
+
+use serde::{Deserialize, Serialize};
+
+//--- Versions
+
+pub mod v1;
+
+//--- Helpers
+
+mod datetime;
+
+//----------- VersionedSpec ----------------------------------------------------
+
+/// A versioned policy file specification.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case", tag = "version")]
+pub enum VersionedSpec {
+    /// The version 1 format.
+    V1(v1::Spec),
+}
+
+// TODO(idea @bal-e): Define a version-independent policy file specification?
+// - Would be called `Spec`.
+// - Initially reuse definitions from `v1`.
+// - `Spec` could be converted to and from `VersionedSpec` explicitly.
+//   - Convert from any version, always build the latest version.
+// - Maybe also provide conversions to and from every individual version.
+//   - Conversions _to_ individual versions might need to be fallible.
+//   - Unclear if conversion to the latest version can/should be fallible.
+// - It would let users write policy files without locking themselves to a
+//   particular version.