[nexus] allow reconfiguring auto-restart policies (#6743)

This commit extends the `instance-reconfigure` API endpoint added in
#6585 to also allow setting instance auto-restart policies (as added in
#6503).

I've also added the actual auto-restart policy to the external API
instance view, along with the boolean `auto_restart_enabled` added in
#6503. This way, it's possible to change just the boot disk by providing
the current auto-restart policy in an instance POST.

common/src/api/external/mod.rs

@@ -1215,6 +1215,20 @@ pub struct InstanceAutoRestartStatus {
     #[serde(rename = "auto_restart_enabled")]
     pub enabled: bool,
 
+    /// The auto-restart policy configured for this instance, or `None` if no
+    /// explicit policy is configured.
+    ///
+    /// If this is not present, then this instance uses the default auto-restart
+    /// policy, which may or may not allow it to be restarted. The
+    /// `auto_restart_enabled` field indicates whether the instance will be
+    /// automatically restarted.
+    //
+    // Rename this field, as the struct is `#[serde(flatten)]`ed into the
+    // `Instance` type, and we would like the field to be prefixed with
+    // `auto_restart`.
+    #[serde(rename = "auto_restart_policy")]
+    pub policy: Option<InstanceAutoRestartPolicy>,
+
     /// The time at which the auto-restart cooldown period for this instance
     /// completes, permitting it to be automatically restarted again. If the
     /// instance enters the `Failed` state, it will not be restarted until after
@@ -1233,7 +1247,9 @@ pub struct InstanceAutoRestartStatus {
 
 /// A policy determining when an instance should be automatically restarted by
 /// the control plane.
-#[derive(Copy, Clone, Debug, Deserialize, Serialize, JsonSchema)]
+#[derive(
+    Copy, Clone, Debug, Deserialize, Serialize, JsonSchema, Eq, PartialEq,
+)]
 #[serde(rename_all = "snake_case")]
 pub enum InstanceAutoRestartPolicy {
     /// The instance should not be automatically restarted by the control plane

nexus/db-model/src/instance.rs

@@ -537,4 +537,9 @@ mod optional_time_delta {
 pub struct InstanceUpdate {
     #[diesel(column_name = boot_disk_id)]
     pub boot_disk_id: Option<Uuid>,
+
+    /// The auto-restart policy for this instance. If this is `None`, it will
+    /// set the instance's auto-restart policy to `NULL`.
+    #[diesel(column_name = auto_restart_policy)]
+    pub auto_restart_policy: Option<InstanceAutoRestartPolicy>,
 }