If I'm merging a silo, org, and project policy on the client in order to give a complete picture of the IAM situation for a project, I need to be able to fetch the current silo policy. Right now we have /policy for fleet policy and /silos/{silo_name}/policy for silo policy. But on the client I don't have the current silo name, or even the silo ID, so I have no way of fetching the silo policy. Here are some ways we might make that possible.

Decent options

• Move existing Fleet /policy to /global/policy, have /policy return the policy for the current silo
  • This is the best option for the client and seems most correct in general, but it may be blocked on the PR that does the /global thing for all the relevant endpoints (early draft here), and it turns out that is a ton of work
• Add /session/silo/policy or /session/policy or /silo/policy or something that returns the policy for the current silo
  • Same as above from client POV
  • Faster because not blocked on /global work
  • Trivial to switch server and client to use /policy once /global work is done

Bad options

• Add silo ID to /session/me and add /by-id/silos/{silo_id} endpoint
  • Client gets silo ID from /session/me, uses it to fetch silo, uses silo name to fetch policy
• Add silo ID to /session/me and /by-id/silos/{silo_id}/policy
  • Client gets silo ID from /session/me, uses it to fetch policy directly. also 🤮 but it's one fewer request
• Add silo name to /session/me, use existing /silos/{silo_name}/policy
  • Not great because while SiloUser has silo_id on it (see below), it does not have silo_name, and this is a pretty silly reason for a join
    

    omicron/nexus/db-model/src/silo_user.rs

    Lines 14 to 18 in aff0d7a

    	pub struct SiloUser {
    	#[diesel(embed)]
    	identity: SiloUserIdentity,
    	pub silo_id: Uuid,