Create minimal admin app

[matheusgomes28]

Create a minimal admin app, which is separate to the main web app. This application should handle all the admin-related tasks such as:

• Adding, modifying, deleting posts.
• Adding, modifying, deleting pages.
• Adding, modifying, deleting menus.
• ...

For the minimal application, let's implement the admin app for managing the posts. It should provide the following endpoints:

• POST /post: add a post.
• PUT /post: update a post.
• DELETE /post: delete a post.