[Feature Request] Allow custom URL/hostname for static hosting

Feature Request

Allow developers to configure a custom subdomain or slug for the static hosting URL when deploying a Rayfin app, instead of the auto-generated random name.

Current Behavior

The hosting URL is auto-generated with a random name:

https://total-alder-ff0fb9a7a5-westcentralus.webapp.msit.fabricapps.net

Format: {random-word}-{random-word}-{hash}-{region}.webapp.{domain}

There is no way to control or change the total-alder portion.

Proposed Solution

Add a hostname or slug option in rayfin.yml under staticHosting:

services:
  staticHosting:
    enabled: true
    folder: dist
    slug: dcx-portal  # <-- custom prefix

This would produce a URL like:

https://dcx-portal-ff0fb9a7a5-westcentralus.webapp.msit.fabricapps.net

Alternatively, support custom domain mapping via the CLI or Fabric portal.

Use Case

• Enterprise teams want recognizable URLs to share with stakeholders
• Random names like total-alder are not meaningful and hard to remember
• Teams need professional-looking URLs for internal portals without setting up external DNS/CNAME records

Workaround

Currently the only option is to set up a CNAME DNS alias externally, which requires coordination with networking teams and isn't always feasible for POC/internal apps.

Environment

• Rayfin CLI: latest
• Deployment target: Fabric MSIT