refactor: move storage controller API structs into pageserver_api (#6927)

## Problem

This is a precursor to adding a convenience CLI for the storage
controller.

## Summary of changes

- move controller api structs into pageserver_api::controller_api to
make them visible to other crates
- rename pageserver_api::control_api to pageserver_api::upcall_api to
match the /upcall/v1/ naming in the storage controller.

Why here rather than a totally separate crate? It's convenient to have
all the pageserver-related stuff in one place, and if we ever wanted to
move it to a different crate it's super easy to do that later.

libs/pageserver_api/src/controller_api.rs

@@ -0,0 +1,129 @@
+use std::str::FromStr;
+
+/// Request/response types for the storage controller
+/// API (`/control/v1` prefix).  Implemented by the server
+/// in [`attachment_service::http`]
+use serde::{Deserialize, Serialize};
+use utils::id::NodeId;
+
+use crate::{models::ShardParameters, shard::TenantShardId};
+
+#[derive(Serialize, Deserialize)]
+pub struct TenantCreateResponseShard {
+    pub shard_id: TenantShardId,
+    pub node_id: NodeId,
+    pub generation: u32,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct TenantCreateResponse {
+    pub shards: Vec<TenantCreateResponseShard>,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct NodeRegisterRequest {
+    pub node_id: NodeId,
+
+    pub listen_pg_addr: String,
+    pub listen_pg_port: u16,
+
+    pub listen_http_addr: String,
+    pub listen_http_port: u16,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct NodeConfigureRequest {
+    pub node_id: NodeId,
+
+    pub availability: Option<NodeAvailability>,
+    pub scheduling: Option<NodeSchedulingPolicy>,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct TenantLocateResponseShard {
+    pub shard_id: TenantShardId,
+    pub node_id: NodeId,
+
+    pub listen_pg_addr: String,
+    pub listen_pg_port: u16,
+
+    pub listen_http_addr: String,
+    pub listen_http_port: u16,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct TenantLocateResponse {
+    pub shards: Vec<TenantLocateResponseShard>,
+    pub shard_params: ShardParameters,
+}
+
+/// Explicitly migrating a particular shard is a low level operation
+/// TODO: higher level "Reschedule tenant" operation where the request
+/// specifies some constraints, e.g. asking it to get off particular node(s)
+#[derive(Serialize, Deserialize, Debug)]
+pub struct TenantShardMigrateRequest {
+    pub tenant_shard_id: TenantShardId,
+    pub node_id: NodeId,
+}
+
+#[derive(Serialize, Deserialize, Clone, Copy, Eq, PartialEq)]
+pub enum NodeAvailability {
+    // Normal, happy state
+    Active,
+    // Offline: Tenants shouldn't try to attach here, but they may assume that their
+    // secondary locations on this node still exist.  Newly added nodes are in this
+    // state until we successfully contact them.
+    Offline,
+}
+
+impl FromStr for NodeAvailability {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "active" => Ok(Self::Active),
+            "offline" => Ok(Self::Offline),
+            _ => Err(anyhow::anyhow!("Unknown availability state '{s}'")),
+        }
+    }
+}
+
+/// FIXME: this is a duplicate of the type in the attachment_service crate, because the
+/// type needs to be defined with diesel traits in there.
+#[derive(Serialize, Deserialize, Clone, Copy, Eq, PartialEq)]
+pub enum NodeSchedulingPolicy {
+    Active,
+    Filling,
+    Pause,
+    Draining,
+}
+
+impl FromStr for NodeSchedulingPolicy {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "active" => Ok(Self::Active),
+            "filling" => Ok(Self::Filling),
+            "pause" => Ok(Self::Pause),
+            "draining" => Ok(Self::Draining),
+            _ => Err(anyhow::anyhow!("Unknown scheduling state '{s}'")),
+        }
+    }
+}
+
+impl From<NodeSchedulingPolicy> for String {
+    fn from(value: NodeSchedulingPolicy) -> String {
+        use NodeSchedulingPolicy::*;
+        match value {
+            Active => "active",
+            Filling => "filling",
+            Pause => "pause",
+            Draining => "draining",
+        }
+        .to_string()
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct TenantShardMigrateResponse {}