Create custom rest resource endpoint to POST data into system.
/**
* Provides a resource to get view modes by entity and bundle.
*
* @RestResource(
* id = "custom_rest_resource",
* label = @Translation("Custom rest resource"),
* uri_paths = {
* "canonical" = "/api/your_endpoint",
* "https://www.drupal.org/link-relations/create" = "/api/your_endpoint"
* }
* )
*/