Do we need additional features?

From prometheus middleware experience I assume there will be some people that want custom metrics support or disable/replace built-in metrics.

Additional metrics can be incremented in echootel.Config.MetricAttributes callback and Metrics attributes can be modified/added in that same callback. This is not very elequant solution but maybe we do not anything more complex than this

	e.Use(echootel.NewMiddlewareWithConfig(echootel.Config{
		MetricAttributes: func(c *echo.Context, v *echootel.Values, attr []attribute.KeyValue) []attribute.KeyValue {
			// increment a metric here
			return append(attr, attribute.String("custom_attr", "value"))
		},
	}))

edit:

custom metrics can be provided by implementing this interface