Add "showmigrations" task to invoke (#7482) (#7484)

- Helpful for debugging user installs

(cherry picked from commit 442f2594d0)

Co-authored-by: Oliver <oliver.henry.walters@gmail.com>

tasks.py

@@ -454,6 +454,12 @@ def migrate(c):
     print('InvenTree database migrations completed!')
 
 
+@task(help={'app': 'Specify an app to show migrations for (leave blank for all apps)'})
+def showmigrations(c, app=''):
+    """Show the migration status of the database."""
+    manage(c, f'showmigrations {app}', pty=True)
+
+
 @task(
     post=[clean_settings, translate_stats],
     help={