Add coordinator defaults + New extra work fields + Cohort cache

Description

• Add a cohort cache
• Adds additional extra work fields: Contract Name, Start/End Date, Baan-Code
• Allows a coordinator to set defaults for:
  • Contract Start/End Date
  • Contract Baan-Code
  • Job Offer Application Deadline

Related Issues

• Resolves #85 (closed)
• Resolves #96 (closed)
• Resolves #97 (closed)
• Resolves #98 (closed)

Checklist

• I have added a changelog entry to reflect the significant changes I made.