groups: expose /readers, /writers channel permissions scries

[mikolajpp]

Summary

Recent experiments with bots revealed a need for a scry endpoint to return a set of ships with read of write permissions to a channel.

Changes

1. Add a /groups/$group-id/channels/$channel-id/readers scry to return a set of ships with read permissions.
2. Add a /groups/$group-id/writers/$channel-id/readers scry to return a set of ships with write permissions.

How did I test?

Tested the scries in a group with two ships and a channel.

Risks and impact

• Safe to rollback without consulting PR author? No, bots might lose access to some of their skills which depend on these endpoints.

• Affects important code area:

  • Onboarding
  • State / providers
  • Message sync
  • Channel display
  • Notifications
  • Other:

Rollback plan

Revert.

[wca4a]

Can comment heavily in the code describing what each of these does so the bots can understand?