archive: Implement height, hashByHeight and call (#1582)

This PR implements:
- `archive_unstable_finalized_height`: Get the height of the most recent
finalized block
- `archive_unstable_hash_by_height`: Get the hashes (possible empty) of
blocks from the given height
- `archive_unstable_call`: Call into the runtime of a block

Builds on top of: https://github.com/paritytech/polkadot-sdk/pull/1560

### Testing Done
- unit tests for the methods with custom block tree for different
heights / forks

Closes: https://github.com/paritytech/polkadot-sdk/issues/1510
Closes: https://github.com/paritytech/polkadot-sdk/issues/1513
Closes: https://github.com/paritytech/polkadot-sdk/issues/1511

@paritytech/subxt-team

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Sebastian Kunert <skunert49@gmail.com>

substrate/client/rpc-spec-v2/src/archive/error.rs

@@ -0,0 +1,66 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! Error helpers for `archive` RPC module.
+
+use jsonrpsee::{
+	core::Error as RpcError,
+	types::error::{CallError, ErrorObject},
+};
+
+/// ChainHead RPC errors.
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+	/// Invalid parameter provided to the RPC method.
+	#[error("Invalid parameter: {0}")]
+	InvalidParam(String),
+	/// Runtime call failed.
+	#[error("Runtime call: {0}")]
+	RuntimeCall(String),
+	/// Failed to fetch leaves.
+	#[error("Failed to fetch leaves of the chain: {0}")]
+	FetchLeaves(String),
+}
+
+// Base code for all `archive` errors.
+const BASE_ERROR: i32 = 3000;
+/// Invalid parameter error.
+const INVALID_PARAM_ERROR: i32 = BASE_ERROR + 1;
+/// Runtime call error.
+const RUNTIME_CALL_ERROR: i32 = BASE_ERROR + 2;
+/// Failed to fetch leaves.
+const FETCH_LEAVES_ERROR: i32 = BASE_ERROR + 3;
+
+impl From<Error> for ErrorObject<'static> {
+	fn from(e: Error) -> Self {
+		let msg = e.to_string();
+
+		match e {
+			Error::InvalidParam(_) => ErrorObject::owned(INVALID_PARAM_ERROR, msg, None::<()>),
+			Error::RuntimeCall(_) => ErrorObject::owned(RUNTIME_CALL_ERROR, msg, None::<()>),
+			Error::FetchLeaves(_) => ErrorObject::owned(FETCH_LEAVES_ERROR, msg, None::<()>),
+		}
+		.into()
+	}
+}
+
+impl From<Error> for RpcError {
+	fn from(e: Error) -> Self {
+		CallError::Custom(e.into()).into()
+	}
+}