Source

File: wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php

protected function prepare_links( $term ) {
		$base  = $this->namespace . '/' . $this->rest_base;
		$links = array(
			'self'       => array(
				'href' => rest_url( trailingslashit( $base ) . $term->term_id ),
			),
			'collection' => array(
				'href' => rest_url( $base ),
			),
			'about'      => array(
				'href' => rest_url( sprintf( 'wp/v2/taxonomies/%s', $this->taxonomy ) ),
			),
		);

		if ( $term->parent ) {
			$parent_term = get_term( (int) $term->parent, $term->taxonomy );

			if ( $parent_term ) {
				$links['up'] = array(
					'href'       => rest_url( trailingslashit( $base ) . $parent_term->term_id ),
					'embeddable' => true,
				);
			}
		}

		$taxonomy_obj = get_taxonomy( $term->taxonomy );

		if ( empty( $taxonomy_obj->object_type ) ) {
			return $links;
		}

		$post_type_links = array();

		foreach ( $taxonomy_obj->object_type as $type ) {
			$post_type_object = get_post_type_object( $type );

			if ( empty( $post_type_object->show_in_rest ) ) {
				continue;
			}

			$rest_base         = ! empty( $post_type_object->rest_base ) ? $post_type_object->rest_base : $post_type_object->name;
			$post_type_links[] = array(
				'href' => add_query_arg( $this->rest_base, $term->term_id, rest_url( sprintf( 'wp/v2/%s', $rest_base ) ) ),
			);
		}

		if ( ! empty( $post_type_links ) ) {
			$links['https://api.w.org/post_type'] = $post_type_links;
		}

		return $links;
	}