Test token strategy that signs JWTs with a local RSA key from priv/keys/key.pem.

Activated by setting config :kinde, test_strategy: true (typically in config/test.exs). Bypasses JWKS endpoint verification so tests can run without network access.

Use sign/1 to generate valid test tokens:

claims = %{"sub" => "kp_abc123", "email" => "test@example.com"}
{:ok, token} = Kinde.Test.TokenStrategy.sign(claims)