use calendars rather than enrollments for tenant lea ownership

[ejoranlienea]

Description & motivation

In rare cases, we need to identify which LEAs are actually members of a tenant. While we were doing this via enrollment records, these can be unpopulated at the start of the school year, while calendars should be populated immediately.

Breaking changes introduced by this PR:

PR Merge Priority:

• Low
• Medium
• High

Changes to existing files:

Switch the base table for tenant-lea attribution

New files created:

Tests and QC done:

edu_wh PR Review Checklist:

Make sure the following have been completed before approving this PR:

• Description of changes has been added to Unreleased section of CHANGELOG.md. Add under ## New Features for features, etc.
• If a new configuration xwalk was added:
  • The code is written such that the xwalk is optional (preferred), and this behavior was tested, OR
  • The code is written such that the xwalk is required, and the required xwalk is added to edu_project_template, and this PR is flagged as breaking change (not for patch release)
  • A description for the new xwalk has been added to EDU documentation site here
• If a new configuration variable was added:
  • The code is written such that the variable is optional (preferred), and this behavior was tested, OR
  • The code is written such that the variable is required, and a default value was added to edu_project_template, and this PR is flagged as breaking change (not for patch release)
  • A description for the new variable has been added to EDU documentation site here
• Reviewer confirms the grain of all tables are unchanged, OR any changes are expected, communicated, and this PR is flagged as a breaking change (not for patch release)