[FE] Multiple value streams: Create new value stream MVC

This is the frontend portion for creating a new value stream. backend work is being tracked in #222337 (closed)

Problem to Solve

This issue focuses on allowing users to create new value streams:

• Broken down from: #219106 (closed)
• Job-to-be-done:
  • Create a saved view: When managing multiple value streams within a mono-repo, I would like to create and save a view of my value stream, so that I can come back to it regularly.

Intended users

• Parker (Product Manager)
• Delaney (Development Team Lead)

Solution

• MVC will initially focus on creating a new Value Stream by duplicating our default template (e.g. plan -> monitor)
• User flow see Figma prototype:
  1. "Create new value stream"
     • If there aren't multiple value streams, display Create new value stream button
     • If there multiple value streams, display Create new value stream as an option in the dropdown section
  2. Pop up a modal to confirm and capture name
  3. Display new value stream with toast message (3000ms) to confirm creation
• Switching between multiple value streams is handled in: #221204 (closed)

Button	Modal	Toast

See Figma file

Permissions and Security

• Permissions for creating new Value Streams is the same as those for configuring them generally.

Feature Flag

• Make available to gitlab-org group on gitlab.com
• Make more broadly available after we get feedback from internal users and addressed any concerns about scale

What does success look like, and how can we measure that?

• Adoption and qualitative feedback from internal users
• Identify issues with VSA calculations, missing features, configuration options & new feature ideas

What is the type of buyer?

• This feature will be made available in GitLab Ultimate