BED-4853: Added feature flag for OIDC initiative

[iustinum]

Description

Added feature flag for enabling OIDC support in migration file for v6.0.0 release

Motivation and Context

This PR addresses: BED-4853

How Has This Been Tested?

Manually tested and verified table records from pgadmin console after database refresh.

Screenshots (optional):

Types of changes

• Database Migrations

Checklist:

• [X] I have met the contributing prerequisites
  • Assigned myself to this PR
  • Added the appropriate labels
  • Associated an issue: https://github.com/SpecterOps/BloodHound/issues/672
  • Read the Contributing guide: https://github.com/SpecterOps/BloodHound/wiki/Contributing
• [X] I have ensured that related documentation is up-to-date
  • Open API docs
  • Code comments (GoDocs / JSDocs)
• [X] I have followed proper test practices
  • Added/updated tests to cover my changes
  • All new and existing tests passed