[SAY-5]

Fixes #447.

peek_header/1 and peek_claims/1 are spec'd as {:ok, claims} | {:error, error_reason}, but they bind JOSE.json_module().decode/1 directly in the with. On OTP's :json backend that call raises on a segment that base64-decodes to invalid JSON (e.g. Joken.peek_claims("invalid.jwt.token")), so the exception escapes the else clause instead of becoming {:error, :token_malformed}:

** (ErlangError) Erlang error: {:invalid_byte, 143}: invalid byte 16#8F at byte position 0
    (joken 2.6.2) lib/joken.ex:156: Joken.peek_claims/1

This wraps the JSON decode in a small safe_json_decode/1 helper that returns :error on a decode exception, matching the tagged {:decode64, _} handling already in these functions. The happy path is unchanged and still does a single decode, so peek_* stays fast (per the note in #447) while honouring its {:error, :token_malformed} contract for malformed input.

[victorolinasc]

This was fixed on #447 and already released as a new version.

Thanks!