🗃️ Add account relationships

DysonNetwork.Sphere/Account/Relationship.cs

@@ -0,0 +1,18 @@
+namespace DysonNetwork.Sphere.Account;
+
+public enum RelationshipType
+{
+    Friend,
+    Blocked
+}
+
+public class Relationship : ModelBase
+{
+    public long FromAccountId { get; set; }
+    public Account FromAccount { get; set; } = null!;
+
+    public long ToAccountId { get; set; }
+    public Account ToAccount { get; set; } = null!;
+
+    public RelationshipType Type { get; set; }
+}