Programmatically add canonical, shortlink, viewport and robots in site header.

For add Programmatically, first we will work on .theme file, we will create alter attachments in .theme file like 'theme_name_page_attachments_alter(array &$page).
Code for add 'viewport' in html head is..
<?php
function theme name/module name_page_attachments_alter(array &$page) {
    $viewport = [
      '#type' => 'html_tag',
      '#tag' => 'meta',
      '#attributes' => [
        'name' => 'viewport',
        'content' => 'width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no',
      ],
    ];
    $page['#attached']['html_head'][] = [$viewport, 'viewport'];

global $base_url;
$current_page = \Drupal::request()->getpathInfo();   
$canon_url = $base_url.''.$current_page;  
  
Code for add 'canonical' in html head is..
    $viewport_canonical = [
      '#type' => 'html_tag',
      '#tag' => 'link',
      '#attributes' => [
        'rel' => 'canonical',
        'href' => $canon_url,
      ],
    ];
    $page['#attached']['html_head'][] = [$viewport_canonical, 'canonical'];   

Code for add 'shortlink' in html head is..
    $viewport_shortlink = [
      '#type' => 'html_tag',
      '#tag' => 'link',
      '#attributes' => [
        'rel' => 'shortlink',
        'href' => $canon_url,
      ],
    ];
    $page['#attached']['html_head'][] = [$viewport_shortlink, 'shortlink'];       
       

For add robots programmatically on site header, we have to work on 'theme_name_preprocess_html(&$variables).
Code for add 'robots' in html head is..
    $noindex = [
        '#tag' => 'meta',
        '#attributes' => [
            'name' => 'robots',
            'content' => 'noindex, nofollow',
        ],
    ];
    $variables['page']['#attached']['html_head'][] = [$noindex, 'noindex'];     

?>

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