move HTTP utilities in a dedicated package (#2123)

needed by #2068

internal/httpserv/middleware_server_header.go

@@ -0,0 +1,11 @@
+package httpserv
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// MiddlewareServerHeader is a middleware that sets the Server header.
+func MiddlewareServerHeader(ctx *gin.Context) {
+	ctx.Writer.Header().Set("Server", "mediamtx")
+	ctx.Next()
+}