CVE-2025-30204: jwt-go allows excessive memory allocation during header parsing

Function parse.ParseUnverified currently splits (via a call to strings.Split) its argument (which is untrusted data) on periods.

As a result, in the face of a malicious request whose Authorization header consists of Bearer followed by many period characters, a call to that function incurs allocations to the tune of O(n) bytes (where n stands for the length of the function’s argument), with a constant factor of about 16. Relevant weakness: CWE-405: Asymmetric Resource Consumption (Amplification)