OPC # 0001: Extract OPC into standalone repo

ControlPlane.Core/Models/TenantTier.cs

@@ -0,0 +1,21 @@
+using System.Text.Json.Serialization;
+
+namespace ControlPlane.Core.Models;
+
+/// <summary>
+/// Defines the billing and support level for a provisioned tenant.
+/// The tier gates which ComponentMode values are available per component in the StackConfig.
+///
+/// Trial      - ephemeral sandbox, all-in-one image, no persistent data guarantee.
+/// Shared     - real production data, shared platform infrastructure (logical slices only).
+/// Dedicated  - full container isolation per component, still on ControlPlane's shared host.
+/// Enterprise - full VM isolation per component (VpsDocker or VpsBareMetal), Pulumi provisioned.
+/// </summary>
+[JsonConverter(typeof(JsonStringEnumConverter))]
+public enum TenantTier
+{
+    Trial,
+    Shared,
+    Dedicated,
+    Enterprise
+}