Add Transparent Proxy and PROXY v2 support and help page

schema.sql

@@ -47,7 +47,9 @@ CREATE TABLE IF NOT EXISTS clients (
 -- Patch graph. type: client_source, client_sink, public_sink, splitter,
 -- tunnel_source, tunnel_sink. host: service address (sources) / bind address
 -- (sinks). Tunnel nodes use iface; their client_id NULL means the target.
--- Databases created before iface existed are migrated by both programs.
+-- origin (sinks): '' | 'proxy_v2' (PROXY v2 header to the service) |
+-- 'transparent' (source spoofing, source must be on a client).
+-- Databases created before iface/origin existed are migrated by both programs.
 CREATE TABLE IF NOT EXISTS nodes (
     id        INTEGER PRIMARY KEY,
     type      TEXT NOT NULL,
@@ -57,6 +59,7 @@ CREATE TABLE IF NOT EXISTS nodes (
     proto     TEXT NOT NULL DEFAULT 'tcp',
     label     TEXT NOT NULL DEFAULT '',
     iface     TEXT NOT NULL DEFAULT '',
+    origin    TEXT NOT NULL DEFAULT '',
     x         REAL NOT NULL DEFAULT 0,
     y         REAL NOT NULL DEFAULT 0
 );