BED-5311 fix: incorrect oidc cookie consumption

[mistahj67]

Description

• Always delete auth cookies in callback
• Fix incorrect sameSite flag for OIDC cross-site cookies

Motivation and Context

This PR addresses: BED-5311

Why is this change required? What problem does it solve?
One cannot login via OIDC in it's current state

How Has This Been Tested?

Locally against a self-signed cert to mimic prod as closely as possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

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

[zinic]

Nothing stands out. Some good refactor in here as well. Pull!