Update the card components to check a dbi_server existence by the id.

lib/decentralised_book_index_web/components/my_components/author_card.ex

@@ -10,7 +10,7 @@ defmodule DecentralisedBookIndexWeb.Components.MyComponents.AuthorCard do
   def author_card(assigns) do
     ~H"""
     <div class="w-full max-w-sm bg-slate-100 border border-gray-200 rounded-lg shadow-sm dark:bg-gray-800 dark:border-gray-700 mx-auto my-3">
-      <%= if @current_user != nil and Role.can_moderate?(@current_user.role) and is_nil(@author.dbi_server) do %>
+      <%= if @current_user != nil and Role.can_moderate?(@current_user.role) and is_nil(@author.dbi_server_id) do %>
         <div class="flex justify-end px-4 pt-4">
           <button
             id={"dropdownButton#{@author.id}"}

lib/decentralised_book_index_web/components/my_components/book_card.ex

@@ -10,7 +10,7 @@ defmodule DecentralisedBookIndexWeb.Components.MyComponents.BookCard do
   def book_card(assigns) do
     ~H"""
     <div class="w-full max-w-sm bg-slate-100 border border-gray-200 rounded-lg shadow-sm dark:bg-gray-800 dark:border-gray-700 mx-auto my-3">
-      <%= if @current_user != nil and Role.can_moderate?(@current_user.role) and is_nil(@book.dbi_server) do %>
+      <%= if @current_user != nil and Role.can_moderate?(@current_user.role) and is_nil(@book.dbi_server_id) do %>
         <div class="flex justify-end px-4 pt-4">
           <button
             id={"dropdownButton#{@book.id}"}