Lets SoulSync sit behind Authelia/Authentik/oauth2-proxy as the gatekeeper: when
security.auth_proxy_header names a header (e.g. Remote-User), a request carrying it
is treated as already-authenticated and passes the launch lock — the proxy did the
login (with 2FA).
- core/security/auth_proxy.py: trusted_proxy_user(get_header, header_name) — returns
the user iff the configured header is present + non-empty; empty header name (the
default) → always None → feature off.
- _enforce_launch_pin ORs it into pin_verified. OFF by default, so a direct install
is unaffected AND a client-spoofed header does nothing unless the operator opted in.
- Doc'd in Support/REVERSE-PROXY.md with the must-strip-client-headers warning.
This is the lightweight Tier 3 (auth-proxy integration), not a full per-user login —
the proxy owns identity; SoulSync trusts it.
Tests: helper off/on/blank/exception-safe; integration — trusted header passes the
gate, no header is locked, and (the safety pin) a spoofed header is IGNORED when the
feature is off. 6 tests pass.
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