Fixes after review

- Maybe it could be rephrased to "attribute name prefixed with X-Attribute-"
- Maybe it worth renaming to userAttributeHeaderPrefix
- Requirement for having only one file uploaded at a time has to be reflected in documentation.
- Maybe this should be reflected in doc
- I'm not sure if missing timestamp attribute should be forced on gateway level. Normally it should be set by app and there should be a way not to set it.

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>

README.md

@@ -1,7 +1,9 @@
 # NeoFS HTTP Gate
 
 NeoFS HTTP Gate is example of tool that provides basic interactions with NeoFS.
-You can download files from NeoFS Network using NeoFS Gate. 
+
+- you can download one file per request from NeoFS Network using NeoFS Gate
+- you can upload one file per request into NeoFS Network using NeoFS Gate 
 
 ## Notable make targets
 
@@ -24,6 +26,11 @@ You can download files from NeoFS Network using NeoFS Gate.
 
 ```go get -u github.com/nspcc-dev/neofs-http-gate```
 
+## File uploading behaviors
+
+- you can upload on file per request
+- if `FileName` not provided by Header attributes, multipart/form filename will be used instead
+
 ## Configuration
 
 ```
@@ -64,6 +71,8 @@ of Timeout and if no activity is seen even after that the connection is closed
 HTTP_GW_KEEPALIVE_PERMIT_WITHOUT_STREAM=Bool - if true, client sends keepalive pings even with no active RPCs.
 If false, when there are no active RPCs, Time and Timeout will be ignored and no keepalive pings will be sent.
 
+HTTP_GW_UPLOAD_HEADER_USE_DEFAULT_TIMESTAMP=bool - enable/disable adding current timestamp attribute when object uploads
+
 Peers preset:
 
 HTTP_GW_PEERS_[N]_ADDRESS = string
@@ -71,6 +80,10 @@ HTTP_GW_PEERS_[N]_WEIGHT = 0..1 (float)
 
 Upload Header Table:
 
-HTTP_GW_UPLOADER_HEADER_[N]_KEY = string - HTTP Header attribute name (except `X-Attribute-`)
+HTTP_GW_UPLOADER_HEADER_[N]_KEY = string - HTTP Header attribute name prefixed with `X-Attribute-`
 HTTP_GW_UPLOADER_HEADER_[N]_VAL = string - NeoFS Object attribute mapping
+
+# By default we had next headers:
+- FileName - to set object filename attribute
+- Timestamp - to set object timestamp attribute
 ```

app.go

@@ -33,6 +33,8 @@ type (
 
 		jobDone chan struct{}
 		webDone chan struct{}
+
+		enableDefaultTimestamp bool
 	}
 
 	App interface {
@@ -78,6 +80,8 @@ func newApp(ctx context.Context, opt ...Option) App {
 
 	a.hdr = newHeaderFilter(a.log, a.cfg)
 
+	a.enableDefaultTimestamp = a.cfg.GetBool(cfgUploaderHeaderEnableDefaultTimestamp)
+
 	a.wlog = logger.GRPC(a.log)
 
 	if a.cfg.GetBool(cmdVerbose) {

filter.go

@@ -22,7 +22,7 @@ type (
 	}
 )
 
-const userAttributeHeader = "X-Attribute-"
+const userAttributeHeaderPrefix = "X-Attribute-"
 
 func newHeaderFilter(l *zap.Logger, v *viper.Viper) HeaderFilter {
 	filter := &headerFilter{
@@ -58,7 +58,7 @@ func newHeaderFilter(l *zap.Logger, v *viper.Viper) HeaderFilter {
 
 func (h *headerFilter) Filter(header *fasthttp.RequestHeader) map[string]string {
 	result := make(map[string]string)
-	prefix := []byte(userAttributeHeader)
+	prefix := []byte(userAttributeHeaderPrefix)
 
 	header.VisitAll(func(key, val []byte) {
 		if len(key) == 0 || len(val) == 0 {

settings.go

@@ -54,9 +54,10 @@ const (
 	cfgLoggerSamplingThereafter = "logger.sampling.thereafter"
 
 	// Uploader Header
-	cfgUploaderHeader    = "uploader_header"
-	cfgUploaderHeaderKey = "key"
-	cfgUploaderHeaderVal = "val"
+	cfgUploaderHeader                       = "uploader_header"
+	cfgUploaderHeaderKey                    = "key"
+	cfgUploaderHeaderVal                    = "val"
+	cfgUploaderHeaderEnableDefaultTimestamp = "upload_header.use_default_timestamp"
 
 	// Peers
 	cfgPeers = "peers"
@@ -144,6 +145,9 @@ func settings() *viper.Viper {
 	v.SetDefault(cfgWebWriteTimeout, time.Minute)
 	v.SetDefault(cfgWebConnectionPerHost, 10)
 
+	// upload header
+	v.SetDefault(cfgUploaderHeaderEnableDefaultTimestamp, false)
+
 	if err := v.BindPFlags(flags); err != nil {
 		panic(err)
 	}

upload.go

@@ -124,8 +124,8 @@ func (a *app) upload(c *fasthttp.RequestCtx) {
 		attributes = append(attributes, filename)
 	}
 
-	// Attribute Timestamp wasn't set from header
-	if _, ok := filtered[object.AttributeTimestamp]; ok {
+	// Attribute Timestamp wasn't set from header and enabled by settings
+	if _, ok := filtered[object.AttributeTimestamp]; ok && a.enableDefaultTimestamp {
 		timestamp := object.NewAttribute()
 		timestamp.SetKey(object.AttributeTimestamp)
 		timestamp.SetValue(strconv.FormatInt(time.Now().Unix(), 10))