config: fix references to Danbooru.config.app_name.

Danbooru.config.app_name is either Safebooru or Danbooru. Fix some
places where it should always be Danbooru.

app/helpers/user_upgrades_helper.rb

@@ -8,7 +8,7 @@ module UserUpgradesHelper
         <script
           src="https://checkout.stripe.com/checkout.js" class="stripe-button"
           data-key="#{Danbooru.config.stripe_publishable_key}"
-          data-name="#{Danbooru.config.app_name}"
+          data-name="#{Danbooru.config.canonical_app_name}"
           data-description="#{desc}"
           data-label="#{desc}"
           data-amount="#{cost}">

app/logical/cloudflare_service.rb

@@ -17,7 +17,7 @@ class CloudflareService
     Danbooru.config.httparty_options.deep_merge(headers: {
       "Authorization" => "Bearer #{api_token}",
       "Content-Type" => "application/json",
-      "User-Agent" => "#{Danbooru.config.app_name}/#{Rails.application.config.x.git_hash}"
+      "User-Agent" => "#{Danbooru.config.canonical_app_name}/#{Rails.application.config.x.git_hash}"
     })
   end
 

app/views/posts/partials/index/_posts.html.erb

@@ -14,7 +14,7 @@
       <% end %>
 
       <% if post_set.safe_posts.present? %>
-        <%= post_set.safe_posts.size %> post(s) on this page were hidden by safe mode (<%= Danbooru.config.app_name %>). Go to <%= link_to "Danbooru", "https://danbooru.donmai.us" %> or disable safe mode to view (<%= link_to_wiki "learn more", "help:user_settings" %>).<br>
+        <%= post_set.safe_posts.size %> post(s) on this page were hidden by safe mode. Go to <%= link_to "Danbooru", "https://danbooru.donmai.us" %> or disable safe mode to view them (<%= link_to_wiki "learn more", "help:user_settings" %>).<br>
       <% end %>
     </div>
   <% end %>

app/views/posts/partials/show/_embedded.html.erb

@@ -3,7 +3,7 @@
 <% elsif post.levelblocked? -%>
   <p><%= link_to("You need a gold account to see this image", new_user_upgrade_path) %>.</p>
 <% elsif post.safeblocked? -%>
-  <p>This image is unavailable on safe mode (<%= Danbooru.config.app_name %>). Go to <%= link_to("Danbooru", "https://danbooru.donmai.us") %> or disable safe mode to view (<%= link_to_wiki "learn more", "help:user_settings" %>).</p>
+  <p>This image is unavailable on <%= Danbooru.config.app_name %>. Go to <%= link_to("Danbooru", "https://danbooru.donmai.us") %> or disable safe mode to view (<%= link_to_wiki "learn more", "help:user_settings" %>).</p>
 <% elsif post.is_flash? -%>
   <%= render("posts/partials/show/flash", post: post) -%>
 <% elsif post.is_video? -%>

config/danbooru_default_config.rb

@@ -9,6 +9,10 @@ module Danbooru
       end
     end
 
+    def canonical_app_name
+      "Danbooru"
+    end
+
     def description
       "Find good anime art fast"
     end
@@ -451,7 +455,7 @@ module Danbooru
     # services will fail if you don't set a valid User-Agent.
     def http_headers
       {
-        "User-Agent" => "#{Danbooru.config.app_name}/#{Rails.application.config.x.git_hash}",
+        "User-Agent" => "#{Danbooru.config.canonical_app_name}/#{Rails.application.config.x.git_hash}",
       }
     end