[DRC] - Ability to add optional members

Description

We want the ability to add optional members once a design review is confirmed. This will allow the creator of the design review or admin to add optional members. Additionally, we want users to be able to add themselves as an optional attendee on design reviews.

Acceptance Criteria

• The creator of the design review can add on additional optional members once the design review is confirmed
• A user can add themselves as an optional attendee in a design review

Proposed Solution

Add an option to include additional optional members when editing a DR. To allow users to add themselves as an optional attendee, add a button to add themselves if they are not already included in the DR.

Mocks

No response