feat: add feature flag storage based on Redis and maintenance mode based on feature flag

[sumandas0]

Feature flag storage powered by Redis

Add an Redis based feature flag to apply feature flag without restarting the pod, this will will help us in multiple occasion where we need do this, like to block write functionality but without any delay of the pod restart.

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

Fix #1

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable

[sumandas0]

Add feature flag disable_writes = true

curl --location --request POST 'http://localhost:21000/api/atlas/v2/admin/featureFlag?key=disable_writes&value=true' 

Delete feature flag, disable_writes

curl --location --request DELETE 'http://localhost:21000/api/atlas/v2/admin/featureFlag/disable_writes'