Change to static skin catalog population

BlueLaminate/BlueLaminate.EFCore/Entities/Collection.cs

@@ -0,0 +1,21 @@
+namespace BlueLaminate.EFCore.Entities;
+
+/// <summary>
+/// A source a skin originates from: either an in-game collection (e.g.
+/// "The Dead Hand Collection") or a container/case (e.g. "Glove Case").
+/// </summary>
+public class Collection
+{
+    public int Id { get; set; }
+
+    public string Name { get; set; } = null!;
+
+    /// <summary>Stable id from the CSGO-API catalogue, e.g. "collection-set-community-37"
+    /// or "crate-4288". The natural key.</summary>
+    public string Slug { get; set; } = null!;
+
+    /// <summary>"Collection" or "Container".</summary>
+    public string Type { get; set; } = null!;
+
+    public ICollection<Skin> Skins { get; set; } = new List<Skin>();
+}