dspace_statistics_api/indexer.py: Use UUID

DSpace 6+ uses a UUID for item identifiers instead of an integer so
we need to update the PostgreSQL schema accordingly. Solr still re-
fers to them as "id" in its schema so we don't need to change anyt-
hing there.

dspace_statistics_api/indexer.py

@@ -264,7 +264,7 @@ with DatabaseManager() as db:
         # create table to store item views and downloads
         cursor.execute(
             """CREATE TABLE IF NOT EXISTS items
-                  (id INT PRIMARY KEY, views INT DEFAULT 0, downloads INT DEFAULT 0)"""
+                  (id UUID PRIMARY KEY, views INT DEFAULT 0, downloads INT DEFAULT 0)"""
         )
 
     # commit the table creation before closing the database connection