[AAP-39137] - Add DAB feature-flags endpoint

[zkayyali812]

What is this PR doing:

Adds DAB feature flag list endpoint

Issue: AAP-39137

Reviewers must know:

1. This will be updated after DAB PR is merged in to use official DAB library, not a personal fork.
2. Unit tests should be written to test this endpoint. I could use some help getting these written. I currently added the tests I'd like to add, but commented out. Due to my environment limitations with docker/podman, I am unable to get my testing environment to work as expected locally.

PR Author & Reviewers: Keep or remove backport labels per Backporting Guidelines
Reviewers: Look for sound code, no code smells, docs & test coverage
Merger: When merging, include the Jira issue link in the squashed commit