Moving file response functionality to shared folder (#22226)

* Moving file response functionality to shared folder

* Linter fixes

* Added the attachment serve to shared folder

* Removed the unwanted logs

* import fixes

* Linter fixes

* License added

* Moved UnsafeContentTypes and MediaContentTypes from api4

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

api4/system.go

@@ -22,6 +22,7 @@ import (
 	"github.com/mattermost/mattermost-server/v6/services/cache"
 	"github.com/mattermost/mattermost-server/v6/services/upgrader"
 	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/shared/web"
 )
 
 const (
@@ -122,7 +123,7 @@ func generateSupportPacket(c *Context, w http.ResponseWriter, r *http.Request) {
 	// Send the zip file back to client
 	// We are able to pass 0 for content size due to the fact that Golang's serveContent (https://golang.org/src/net/http/fs.go)
 	// already sets that for us
-	writeFileResponse(outputZipFilename, FileMime, 0, now, *c.App.Config().ServiceSettings.WebserverMode, fileBytesReader, true, w, r)
+	web.WriteFileResponse(outputZipFilename, FileMime, 0, now, *c.App.Config().ServiceSettings.WebserverMode, fileBytesReader, true, w, r)
 }
 
 func getSystemPing(c *Context, w http.ResponseWriter, r *http.Request) {