Bumping ed25519-dalek to v2 and fix broken v1 APIs.

[kengggg]

This pull request updates the ed25519-dalek dependency to version 2 and refactors the key generation logic to align with the new API. The changes primarily involve replacing the deprecated Keypair struct with the new SigningKey and VerifyingKey types, ensuring compatibility with the updated library.

Dependency Update:

• Updated ed25519-dalek dependency from version 1.0.1 to 2 in Cargo.toml. This change ensures the project uses the latest version of the library, which introduces a new API for key generation.

Key Generation Refactor:

• Refactored the generate_key_pair function in src/keygen.rs to replace the deprecated Keypair::generate method with explicit creation of SecretKey, SigningKey, and VerifyingKey. This aligns with the new ed25519-dalek API and ensures compatibility with version 2.
• Updated the generate_openssh_key_pair function in src/keygen.rs to use the new SigningKey and VerifyingKey types for generating OpenSSH-compatible key pairs. Adjusted the handling of raw key bytes and the encoding functions accordingly.

[Copilot]

Pull Request Overview

This PR updates the ed25519-dalek dependency to v2 and refactors the key generation logic to use the new API.

• Updated the dependency version in Cargo.toml.
• Refactored generate_key_pair and generate_openssh_key_pair in src/keygen.rs to use SecretKey, SigningKey, and VerifyingKey.
• Adjusted key byte handling for compatibility with hexadecimal and OpenSSH encoding.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/keygen.rs	Replaced Keypair generation with explicit creation of secret, signing, and verifying keys.
Cargo.toml	Updated the ed25519-dalek dependency from version 1.0.1 to 2.