How to fix duplicate content issues in Grav?

@domenico.weimann 

Fixing duplicate content issues in Grav, a flat-file CMS, involves several strategies:

1. Canonical URLs: Use canonical tags to indicate the preferred version of a page when you have multiple URLs pointing to similar content. This helps search engines understand which version you want indexed. You can set this by editing the Twig templates and adding:
2. Disable Taxonomy Duplicate Content: Sometimes, taxonomy-based routes can create duplicate content. Make sure your taxonomy filters or routes are configured properly to minimize duplicates. You can review and adjust these in your site.yaml.
3. Redirects and Aliases: Use URL redirects to point duplicate pages to the preferred page. Grav supports a redirect header in page Markdown files, and you can also use the .htaccess file for more complex redirects if you're using Apache.
4. Robots.txt: Use the robots.txt file to disallow search engines from crawling non-essential duplicated content. However, don't use this method for essential duplicate content where ranking is a concern.
5. Optimize Page Routing: Ensure your navigation and linking strategies avoid links that produce duplicate content. When linking internally, use absolute paths or ensure all links adhere to a consistent URL structure.
6. Content Organization: Ensure your site structure is organized efficiently to avoid creating various paths to the same content. Revisit your folder structure and page slugs to maintain a clear hierarchy.
7. Pagination and Sorting: Use query parameters for pagination and sorting, making sure to use canonical URLs to point to the main pages.
8. Use of Plugins: Grav offers plugins that can help manage SEO including duplicates, like the "SEO" plugin which offers configuration options to handle many SEO errors.

By employing these strategies, you can minimize and manage duplicate content issues in Grav effectively.