Proper WordPress Plugin Boilerplate (With Class, Options Page, Setting Link, and API Helper Function)

plugin-file.php

<?php 
  
/*
Plugin Name: MYPLUGIN
Description: MYPLUGIN
Version: 1.0.0
Author: MYPLUGIN
Author URI: https://MYPLUGIN.com
Text Domain: myplugin
*/

/*
|--------------------------------------------------------------------------
| CONSTANTS
|--------------------------------------------------------------------------
*/
// plugin version
if(!defined('MYPLUGIN_PLUGIN_VER')) 
{
    define('MYPLUGIN_PLUGIN_VER', '1.0.0');
}
// plugin folder url
if(!defined('MYPLUGIN_PLUGIN_URL')) 
{
    define('MYPLUGIN_PLUGIN_URL', plugin_dir_url( __FILE__ ));
}
// plugin folder path
if(!defined('MYPLUGIN_PLUGIN_PATH')) 
{
    define('MYPLUGIN_PLUGIN_PATH', plugin_dir_path( __FILE__ ));
}

/*
|--------------------------------------------------------------------------
| MAIN CLASS
|--------------------------------------------------------------------------
*/
 if ( !class_exists( 'MYPLUGIN' ) ) 
 {
    class MYPLUGIN
    {
        public static function init() 
        {
            // Hook for shortcode
            add_shortcode('myplugin', array('MYPLUGIN','shortcode')); 
          
            // Add Options Page for plugin
            add_action('admin_menu', array('MYPLUGIN','register_options_page') );
            add_action('admin_init', array('MYPLUGIN','register_settings') );

            // Add settings link to plugins page listing
            $plugin = plugin_basename(__FILE__);
            add_filter("plugin_action_links_$plugin", array('MYPLUGIN', 'add_settings_link') );

            // Enqueue scripts
            add_action( 'wp_enqueue_scripts', array('MYPLUGIN', 'enqueue_scripts') );
          
            // Register Rest Routes
          	add_action('rest_api_init', array('MYPLUGIN', 'register_rest_routes') );
        }

        public static function enqueue_scripts() 
        {
            wp_enqueue_style( 'MYPLUGIN-style', plugins_url( 'css/style.css', __FILE__ ), array(), MYPLUGIN_PLUGIN_VER, 'all');
        }
      
        // Shortcode function
      	public static function shortcode($atts) 
        {
            // override default attributes with user attributes
            $a = shortcode_atts([
                "x" => "y",
            ], $atts);

            $output = '';

            return $output;
        }

        // Settings link on plugin page
        public static function add_settings_link($links)
        {
            $settings_link = '<a href="options-general.php?page=myplugin">' . __('Settings') . '</a>';
            array_push($links, $settings_link);
            return $links;
        }

        // Register Settings For a Plugin so they are grouped together
        public static function register_settings()
        {
            add_option('MYPLUGIN_setting', '');
            register_setting('MYPLUGIN_options_group', 'MYPLUGIN_setting', null);
        }

        // Create an options page
        public static function register_options_page()
        {
            add_options_page('MYPLUGIN Settings', 'MYPLUGIN Settings', 'manage_options', 'MYPLUGIN', array('MYPLUGIN','options_page'));
        }

        // Display Settings on Options Page
        public static function options_page()
        { ?>
                <div>
                    <h2 style="font-size: 2em;">MYPLUGIN Settings</h2>


            
            <form method="post" action="options.php"> 
                <?php settings_fields('MYPLUGIN_options_group'); ?> 

                <input type="text" id="MYPLUGIN_setting" name="MYPLUGIN_setting" value="<?php echo get_option('MYPLUGIN_setting'); ?>" style="width:40%;" />

                <?php submit_button(); ?>
            </form> 
        <?php
        }
      
        public static function register_rest_routes()
        {
          register_rest_route( 'myplugin/v1', 'api-function',array(
            'methods'  => 'POST',
            'callback' => array('MYPLUGIN', 'api_function'),
            'permission_callback' => function() {
              //return current_user_can('edit_posts');
              return true;
            }
          ));
        }

        public static function api_function($response)
        {
          self::write_log('From our API call');
          self::write_log($_POST);
          self::write_log( $response->get_json_params() ); // If payload is sent as a JSON body, this is how you access
        }

        private static function makeApiCall( $url, $payload, $method = 'POST' ) 
        {

			$response = wp_remote_request( $url, array(
				'method'      => $method,
				'timeout'     => 45,
                'redirection' => 5,
				'httpversion' => '1.1',
                'blocking'    => true,
				'headers' => array(
					//'Authorization' => 'Basic ' . base64_encode( 'anystring' . ':' . 'themailchimpapikey-us5' ),
					//'Content-Type' => 'application/json; charset=utf-8',
                    //'Content-Type' => 'multipart/form-data',
                    'Content-Type'   => 'application/x-www-form-urlencoded; charset=utf-8',
				),
				//'body'        => json_encode($payload),
                'body'        => $payload,
				//'data_format' => 'body',
				'cookies'     => array(),
			) );
			if ( is_wp_error( $response )) {
                $error_message = $response->get_error_message();
                return array( false, $error_message );
            } else if ( wp_remote_retrieve_response_code($response) !== 200 ) {
                return array( false, $response );
            } else {
                return array( true, wp_remote_retrieve_body($response) );
			}  
        }

        private static function write_log ( $log ) 
        {
            if ( is_array( $log ) || is_object( $log ) ) {
              error_log( print_r( $log, true ) );
            } else {
              error_log( $log );
            }
        }

    } // End class

    MYPLUGIN::init();
}