HRQB 57 - many-to-one relationships for LibHR table

[ghukill]

Purpose and background context

This PR allows the LibHR Employee Appointments table to have multiple rows for employee and/or headcount ID (HC ID). This allows a headcount ID like L-001 to have multiple rows, where new columns Begin Date and End Date will show when that headcount ID was applied and to whom.

In turn, this supports reports in Quickbase that show the employee's associated with a single headcount ID, vacancy reports, etc.

Includes new or updated dependencies?

YES: cryptography had a required update for safety vulnerability

NOTE: other dependencies were not updated at this time, as updates to mypy and ruff are bringing lots of linting errors. This will be handled in a future maintenance update.

Changes expectations for external applications?

YES: Quickbase receiving new data

What are the relevant tickets?

• https://mitlibraries.atlassian.net/browse/HRQB-57

Developer

• All new ENV is documented in README
• All new ENV has been added to staging and production environments
• All related Jira tickets are linked in commit message(s)
• Stakeholder approval has been confirmed (or is not needed)

Code Reviewer(s)

• The commit message is clear and follows our guidelines (not just this PR message)
• There are appropriate tests covering any new functionality
• The provided documentation is sufficient for understanding any new functionality introduced
• Any manual tests have been performed or provided examples verified
• New dependencies are appropriate or there were no changes