feat: hide sensitive data

feat: hide sensitive data: a task in bird-critic-1.5-full-300 (Harbor dataset). OAuth contexts and credential structs in this SDK carry client secrets and access tokens. Anything that dumps such an object — a print r in a debug branch, an exception dump, a log line, a JSON response assembled from…

The task

OAuth contexts and credential structs in this SDK carry client secrets and access tokens. Anything that dumps such an object — a `print_r` in a debug branch, an exception dump, a log line, a JSON response assembled from the struct — leaks those secrets. Make the sensitive structs refuse to expose their contents…

Part of kochsnow/bird-critic-1.5-full-300.