(new): add log level helpers and HTTP method levels

- move LogLevel and predefined levels into levels.go
- add level-specific constructors for info/warn/error/fatal/debug
- add predefined HTTP method log levels and LogLevelForMethod
- unify Logger Print/Println internals and add Printf
- improve GoDoc coverage for exported APIs

http.go

@@ -0,0 +1,47 @@
+package sneklog
+
+import "net/http"
+
+// HTTP method-specific log levels.
+var (
+	HTTPGetLevel    = NewInfoLogLevelWithColors("get", FgGreen, BgNone)
+	HTTPHeadLevel   = NewInfoLogLevelWithColors("head", FgCyan, BgNone)
+	HTTPPostLevel   = NewInfoLogLevelWithColors("post", FgBlue, BgNone)
+	HTTPPutLevel    = NewInfoLogLevelWithColors("put", FgYellow, BgNone)
+	HTTPPatchLevel  = NewInfoLogLevelWithColors("patch", FgMagenta, BgNone)
+	HTTPDeleteLevel = NewInfoLogLevelWithColors("delete", FgRed, BgNone)
+)
+
+// Additional HTTP method-specific log levels.
+var (
+	HTTPOptionsLevel = NewDebugLogLevelWithColors("options", FgWhite, BgNone)
+	HTTPConnectLevel = NewDebugLogLevelWithColors("connect", FgCyan, BgNone)
+	HTTPTraceLevel   = NewDebugLogLevelWithColors("trace", FgWhite, BgNone)
+	HTTPUnknownLevel = NewDebugLogLevelWithColors("http", FgWhite, BgNone)
+)
+
+// LogLevelForMethod returns the predefined log level associated with an HTTP method.
+func LogLevelForMethod(method string) LogLevel {
+	switch method {
+	case http.MethodGet:
+		return HTTPGetLevel
+	case http.MethodHead:
+		return HTTPHeadLevel
+	case http.MethodPost:
+		return HTTPPostLevel
+	case http.MethodPut:
+		return HTTPPutLevel
+	case http.MethodPatch:
+		return HTTPPatchLevel
+	case http.MethodDelete:
+		return HTTPDeleteLevel
+	case http.MethodOptions:
+		return HTTPOptionsLevel
+	case http.MethodConnect:
+		return HTTPConnectLevel
+	case http.MethodTrace:
+		return HTTPTraceLevel
+	default:
+		return HTTPUnknownLevel
+	}
+}