Add authentication to workspaces_feature_flag_controller

MR: Pending

Description

Created as a followup to this thread.

For background, the workspaces_feature_flag_controller was created as a workaround to address the limitations of the existing feature flag framework to check whether a feature is enabled in the FE code. However, since this API was created to deal with a high priority bug, authentication was skipped because the change had low impact.

However, since this API may be used for other feature flags in the future, it should follow proper authentication procedures to prevent any possible abuse.

Acceptance Criteria

• Add proper authentication to the controller
• Add specs to verify the change

Technical Requirements

Same as acceptance criteria

Design Requirements

NA

Impact Assessment

Adding authentication should not break any existing features that use the workspace_feature_flag API

User Story

NA