Add or update Google Tag Manager

For GiveCampus school settings.

GiveCampus stores separate school-level GTM head and body snippets. The general Analytics and Tracking editor is in GiveCampus-only settings, so school administrators should ask authorized GiveCampus support to add/update the approved snippets for the intended school and environment. Do not direct customers to an employee-only menu or claim all page surfaces use the snippets identically. Verify the relevant public pages after configuration; no live change occurs merely by requesting it.