This update optimizes how Odoo searches for calendar resources, specifically when filtering by user. By adding an index, the system now responds more quickly to these queries, leading to a smoother user experience. This change focuses on internal performance improvements.

This commit adds an index on `planning.calendar.resource.user_id`, as it's the only criteria used in `get_calendar_filters` for the `search_count` and the `search_read` done after.

Forward-Port-Of: odoo/enterprise#113304