Add sr25519 signature scheme

[leonardocustodio]

Hello @wolfmcnally ,
This PR aims to add sr25119 support. This is the default signature type used by Polkadot and any Substrate-compatible blockchain. More info here

[Copilot]

Pull request overview

This PR adds support for the SR25519 (Schnorr-Ristretto) signature scheme, which is commonly used in the Substrate and Polkadot ecosystems. The implementation provides comprehensive support including key generation, signing, verification, and serialization.

Key Changes

• Implements Sr25519PrivateKey and Sr25519PublicKey types with full signing and verification capabilities
• Integrates SR25519 into the existing SigningPrivateKey, SigningPublicKey, and Signature enums
• Adds SR25519 to SignatureScheme enum for consistent key pair generation
• Updates feature flags, tests, and documentation across the codebase

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/sr25519/sr25519_public_key.rs	New file implementing SR25519 public key with verification and serialization
src/sr25519/sr25519_private_key.rs	New file implementing SR25519 private key with signing, key derivation, and seed management
src/sr25519/mod.rs	Module definition and documentation for SR25519 types
src/signing/signing_public_key.rs	Adds Sr25519 variant to SigningPublicKey enum with CBOR encoding support
src/signing/signing_private_key.rs	Adds Sr25519 variant to SigningPrivateKey enum with signing and encoding support
src/signing/signature.rs	Adds Sr25519 signature variant with CBOR encoding and scheme detection
src/signing/signature_scheme.rs	Adds Sr25519 scheme with keypair generation support
src/signing/mod.rs	Adds SR25519 signing tests and updates conditional compilation flags
src/lib.rs	Exports Sr25519PrivateKey and Sr25519PublicKey types
src/public_keys.rs	Updates feature flags to include sr25519
src/private_keys.rs	Updates feature flags to include sr25519
src/keypair.rs	Updates feature flags to include sr25519
Cargo.toml	Adds schnorrkel and blake2 dependencies with sr25519 feature flag, includes in default features
run_tests.sh	Adds test configurations for sr25519 feature combinations
README.md	Documents new Sr25519PrivateKey and Sr25519PublicKey types
CODING.md	Updates documentation checklist to include SR25519 types

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[Copilot]

The conditional compilation in the subsequent not(any(...)) attribute (around line 904-909) is missing feature = "sr25519". This will cause a compilation error when sr25519 is the only feature enabled, since the wildcard pattern will be marked as unreachable but won't actually be unreachable. The encoder documentation should also be updated to mention SR25519 encoding (around line 866-877).

[leonardocustodio]

This doesn't seem to be true:

cargo build --features=sr25519

Works without any compilation issues.