Problem Description:
When a reverse proxy passes authentication headers containing non-ASCII characters (e.g., Chinese usernames), the plugin displays garbled text instead of the correct username. This occurs because the plugin directly reads HTTP header values without accounting for character encoding conversion.

Technical Root Cause:
HTTP specification (RFC 7230) mandates ISO-8859-1 encoding for headers. The plugin currently:

1. Reads header values as raw ISO-8859-1 strings

1. Doesn't provide encoding configuration options

1. Lacks decoding logic for non-ASCII characters