feat: add self-managed token signer

[EHadoux]

Adds the ability to self-sign tokens. Also adds a little helper to decode the token to inspect its content.

[Copilot]

Pull Request Overview

Adds support for self-managed token signing and decoding, enabling users with their own SSO systems to self-sign tokens. Key changes include:

• Updating the README with documentation and usage examples for self-signing tokens.
• Introducing a SelfManagedSigner class and a decode_self_signed_jwt helper in scribeauth.py.
• Adding tests for self-signed token generation and decoding, and updating dependencies in pyproject.toml.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
README.md	Added documentation and examples for self-signing tokens.
scribeauth/scribeauth.py	Added SelfManagedSigner implementation and token decoding helper function.
tests/test_scribeauth.py	Added new tests for self-signed token functionality and updated test helpers.
pyproject.toml	Included pyjwt as a dependency for token signing.
scribeauth/init.py	Exported SelfManagedSigner and decode_self_signed_jwt for public API usage.

Comments suppressed due to low confidence (2)

scribeauth/scribeauth.py:369

• A duplicate definition of SelfManagedSigner appears to be introduced. Ensure that only one implementation exists to avoid conflicts.

@dataclass

scribeauth/scribeauth.py:385

• The docstring is misleading; consider updating it to 'Signs a JWT payload using the private key' or similar to accurately describe the functionality.

        "Signs the private key with the private key."