[Meta] Ubercart 6

This is the plan to migrate Ubercart 6 to Drupal 8 commerce. For a some background see #2894435: [Meta] Commerce Migrate Planning.
The current work, Level 2, is shown at the top for convenience.

Level 2

• Order adjustments - taxes
• Order item adjustments - discounts

Level 3
This is just a list of ubercart modules. It will need to be ordered.

• Product features - Ubercart 'core - optional' #2893391: [Ubercart D6] Migrate product features
• Roles - Ubercart 'core - optional' #2892880: [Ubercart D6] Roles
• File downloads - Ubercart 'core - optional' #2892878: [Ubercart D6] File downloads
• Product kits - Ubercart 'extra' #2893393: [Ubercart D6] Migrate product kits
• Cart #2889792: [Ubercart D6] Migrate cart
• Conditional Actions #2890123: [Ubercart D6] Migrate conditional actions
• Shipping Quotes
• Tax report
• Cart link
• Google analytics
• Stock
• FlatRate
• Us Postal Service
• UPS
• Weight quote
• Catalog - Based on views, which are not migrated. See #2500547: Upgrade path for Views from Drupal 6 and 7
• Reports - No migration required here. The reporting is in Commerce Reporting

The Known issues when upgrading from Drupal 6 or 7 to Drupal 8 might be useful.