add category query

lib/plug_micropub.ex

@@ -122,7 +122,7 @@ defmodule PlugMicropub do
 
   defp get_query(conn) do
     case Map.fetch(conn.query_params, "q") do
-      {:ok, query} when query in ["config", "source", "syndicate-to", "channel"] ->
+      {:ok, query} when query in ["config", "source", "syndicate-to", "channel", "category"] ->
         {:ok, String.to_existing_atom(query)}
 
       _ ->
@@ -200,6 +200,15 @@ defmodule PlugMicropub do
     end
   end
 
+  defp handle_query(:category, access_token, conn) do
+    handler = conn.private[:plug_micropub][:handler]
+
+    case handler.handle_category_query(access_token) do
+      {:ok, content} -> send_content(conn, content)
+      error -> send_error(conn, error)
+    end
+  end
+
   defp handle_query(:source, access_token, conn) do
     with {:ok, url} <- Map.fetch(conn.query_params, "url"),
          do: do_source_query(conn, access_token, url),

lib/plug_micropub/handler_behaviour.ex

@@ -56,6 +56,10 @@ defmodule PlugMicropub.HandlerBehaviour do
               {:ok, map}
               | handler_error
 
+  @callback handle_category_query(access_token) ::
+              {:ok, map}
+              | handler_error
+
   @callback handle_media(file :: Plug.Upload.t(), access_token) ::
               {:ok, url :: String.t()} | handler_error
 end