docs(parsing): add package and symbol doc comments

Add godoc comments for all 62 exported symbols across 20 files in
config/parsing/: 23 MDKey constants, 35 Parse*/List/Default* functions,
3 TLS helpers, 1 Args struct with 7 fields, and the package doc.

config/parsing/parse.go

@@ -1,32 +1,95 @@
+// Package parsing converts user-facing configuration structs into registered
+// runtime components. Each sub-package (service, hop, chain, auth, …) owns the
+// parsing logic for its corresponding core interface.
+//
+// Metadata keys defined below bridge the gap between named config fields and
+// generic key-value metadata. When a value is not represented by an explicit
+// field on a config struct it flows through the metadata system instead and
+// these keys are used to look it up at component Init time.
 package parsing
 
 const (
+	// MDKeyProxyProtocol sets the HAProxy proxy-protocol version on a listener.
 	MDKeyProxyProtocol = "proxyProtocol"
-	MDKeyInterface     = "interface"
-	MDKeySoMark        = "so_mark"
-	MDKeyHash          = "hash"
-	MDKeyPreUp         = "preUp"
-	MDKeyPreDown       = "preDown"
-	MDKeyPostUp        = "postUp"
-	MDKeyPostDown      = "postDown"
-	MDKeyIgnoreChain   = "ignoreChain"
-	MDKeyEnableStats   = "enableStats"
 
-	MDKeyRecorderDirection       = "direction"
+	// MDKeyInterface binds the outbound connection to a specific network interface.
+	MDKeyInterface = "interface"
+
+	// MDKeySoMark sets the SO_MARK socket option on outbound connections.
+	MDKeySoMark = "so_mark"
+
+	// MDKeyHash selects the hash source used by hash-based selectors.
+	MDKeyHash = "hash"
+
+	// MDKeyPreUp is a shell command executed when a service starts listening.
+	MDKeyPreUp = "preUp"
+
+	// MDKeyPreDown is a shell command executed immediately before a service
+	// stops listening.
+	MDKeyPreDown = "preDown"
+
+	// MDKeyPostUp is a shell command executed after a service has successfully
+	// started listening.
+	MDKeyPostUp = "postUp"
+
+	// MDKeyPostDown is a shell command executed after a service has stopped
+	// listening.
+	MDKeyPostDown = "postDown"
+
+	// MDKeyIgnoreChain disables chain routing for a service. When set the
+	// listener/handler will not prepend a chain, which is useful for services
+	// that handle routing themselves (e.g. DNS, TUN).
+	MDKeyIgnoreChain = "ignoreChain"
+
+	// MDKeyEnableStats enables per-service connection statistics collection.
+	MDKeyEnableStats = "enableStats"
+
+	// MDKeyRecorderDirection toggles whether traffic direction (client→server or
+	// server→client) is recorded alongside the payload.
+	MDKeyRecorderDirection = "direction"
+
+	// MDKeyRecorderTimestampFormat sets the timestamp layout used in recorder
+	// output (Go time.Format layout).
 	MDKeyRecorderTimestampFormat = "timeStampFormat"
-	MDKeyRecorderHexdump         = "hexdump"
-	MDKeyRecorderHTTPBody        = "http.body"
+
+	// MDKeyRecorderHexdump enables hexadecimal dump output in recorders.
+	MDKeyRecorderHexdump = "hexdump"
+
+	// MDKeyRecorderHTTPBody enables capturing the HTTP request/response body in
+	// HTTP-based recorders.
+	MDKeyRecorderHTTPBody = "http.body"
+
+	// MDKeyRecorderHTTPMaxBodySize limits the maximum body size (in bytes) that
+	// an HTTP recorder will capture.
 	MDKeyRecorderHTTPMaxBodySize = "http.maxBodySize"
 
+	// MDKeyLimiterRefreshInterval sets how often a limiter reloads its
+	// configuration from an external source.
 	MDKeyLimiterRefreshInterval = "limiter.refreshInterval"
+
+	// MDKeyLimiterCleanupInterval sets how often a limiter purges expired
+	// entries from its internal state.
 	MDKeyLimiterCleanupInterval = "limiter.cleanupInterval"
-	MDKeyLimiterScope           = "limiter.scope"
 
+	// MDKeyLimiterScope controls whether a cached traffic limiter's scope is
+	// per-service ("service") or per-client ("client").
+	MDKeyLimiterScope = "limiter.scope"
+
+	// MDKeyObserverResetTraffic requests a traffic counter reset each time the
+	// observer reports.
 	MDKeyObserverResetTraffic = "observer.resetTraffic"
-	MDKeyObserverPeriod       = "observer.period"
 
-	MDKeyNetns    = "netns"
+	// MDKeyObserverPeriod sets the interval between observer reports.
+	MDKeyObserverPeriod = "observer.period"
+
+	// MDKeyNetns is the network namespace name or path used for the listener
+	// side (inbound).
+	MDKeyNetns = "netns"
+
+	// MDKeyNetnsOut is the network namespace name or path used for the handler
+	// (outbound) side.
 	MDKeyNetnsOut = "netns.out"
 
+	// MDKeyDialTimeout sets the dial timeout for outbound connections.
 	MDKeyDialTimeout = "dialTimeout"
 )