Add onboarding feature flag

[david-livefront]

🎟️ Tracking

N/A

📔 Objective

This PR adds the feature flag for the forthcoming onboarding feature.

Note that the new flag is not yet used.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed
  issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[dseverns-livefront]

[github-actions]

Checkmarx One – Scan Summary & Details – f6a75ea6-0a37-4dd2-a598-682b9e588736

No New Or Fixed Issues Found

[SaintPatrck]

[david-livefront]

Thanks @dseverns-livefront & @SaintPatrck