Add configuration[accounts][max_pinned_statuses] to /api/v2/instance

Also add the absent max_featured_tags to the api spec for /api/v2/instance

lib/pleroma/web/api_spec/operations/instance_operation.ex

@@ -272,6 +272,19 @@ defmodule Pleroma.Web.ApiSpec.InstanceOperation do
           type: :object,
           description: "Instance configuration",
           properties: %{
+            accounts: %Schema{
+              type: :object,
+              properties: %{
+                max_featured_tags: %Schema{
+                  type: :integer,
+                  description: "The maximum number of featured tags allowed for each account."
+                },
+                max_pinned_statuses: %Schema{
+                  type: :integer,
+                  description: "The maximum number of pinned statuses for each account."
+                }
+              }
+            },
             urls: %Schema{
               type: :object,
               properties: %{

lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -213,6 +213,7 @@ defmodule Pleroma.Web.MastodonAPI.InstanceView do
 
   defp configuration2 do
     configuration()
+    |> put_in([:accounts, :max_pinned_statuses], Config.get([:instance, :max_pinned_statuses], 0))
     |> put_in([:statuses, :characters_reserved_per_url], 0)
     |> Map.merge(%{
       urls: %{