Add bungie/domain/roblox connection types and correct SkuFlags.available

[MCausc78]

Description

Connection types:

• Bungie.net: discord/discord-api-spec@d1a4623 and Add bungie connection discord/discord-api-docs#6716
• Domain: docs: document connection type domain discord/discord-api-docs#6395
• roblox: discord/discord-api-spec@526e078
  Sku flags: https://canary.discord.com/developers/docs/monetization/skus#sku-object-sku-flags

Connected issues & other potential problems

none

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• Ran dart analyze or make analyze and fixed all issues
• Ran dart format --set-exit-if-changed -l 160 ./lib or make format and fixed all issues
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works