merge: Expose metrics directly to user (#80)

This pull request adds the ability to access the metrics of resources modeled
by the OpenDC Compute, Workflow, FaaS, and TensorFlow services directly from
their corresponding interfaces. Previously, users would have to interact with
OpenTelemetry to obtain these values, which is complex and provides
significant overhead.

With this pull request, users can access the metrics of all cloud resources
modeled by OpenDC via methods such as `getSchedulerStats()`, etc.

** Breaking Changes **

- `ComputeService.hostCount` removed in favour of `ComputeService.hosts.size`

1 files changed, 7 insertions, 0 deletions

diff --git a/opendc-compute/opendc-compute-api/src/main/kotlin/org/opendc/compute/api/Server.kt b/opendc-compute/opendc-compute-api/src/main/kotlin/org/opendc/compute/api/Server.kt
index b508a9f8..64b73d0b 100644
--- a/opendc-compute/opendc-compute-api/src/main/kotlin/org/opendc/compute/api/Server.kt
+++ b/opendc-compute/opendc-compute-api/src/main/kotlin/org/opendc/compute/api/Server.kt
@@ -22,6 +22,8 @@
 
 package org.opendc.compute.api
 
+import java.time.Instant
+
 /**
  * A stateful object representing a server instance that is running on some physical or virtual machine.
  */
@@ -42,6 +44,11 @@ public interface Server : Resource {
     public val state: ServerState
 
     /**
+     * The most recent moment in time when the server was launched.
+     */
+    public val launchedAt: Instant?
+
+    /**
      * Request the server to be started.
      *
      * This method is guaranteed to return after the request was acknowledged, but might return before the server was