feat(templates): add localized push templates and actions

Share template keys across email and push with independent editors and revisions. Render localized actions and preserve version-one delivery.

Ref: IT-1627

HrynCo.NotificationService.Contracts/Messages/PushActionMetadata.cs

@@ -0,0 +1,6 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+public sealed record PushActionMetadata
+{
+    public string? ObjectId { get; init; }
+}

HrynCo.NotificationService.Contracts/Messages/PushTemplateData.cs

@@ -0,0 +1,7 @@
+namespace HrynCo.NotificationService.Contracts.Messages;
+
+public sealed record PushTemplateData
+{
+    public required IReadOnlyDictionary<string, string> Bindings { get; init; }
+    public required IReadOnlyDictionary<string, PushActionMetadata> Actions { get; init; }
+}

HrynCo.NotificationService.Contracts/Messages/SendPushMessageData.cs

@@ -6,9 +6,12 @@ public sealed record SendPushMessageData
     public required Guid BindingId { get; init; }
     public required Guid UserId { get; init; }
     public required string ServiceName { get; init; }
-    public required string Title { get; init; }
-    public required string Body { get; init; }
+    public string? Title { get; init; }
+    public string? Body { get; init; }
     public string Route { get; init; } = "/home";
+    public string? TemplateKey { get; init; }
+    public string? LanguageCode { get; init; }
+    public PushTemplateData? TemplateData { get; init; }
     public int Version { get; init; } = 1;
     public required DateTimeOffset ExpiresAt { get; init; }
     public string? Token { get; init; }