Objectives ecs rework (#19967)

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Objectives/Systems/RoleRequirementSystem.cs

@@ -0,0 +1,28 @@
+using Content.Server.Objectives.Components;
+using Content.Shared.Objectives.Components;
+
+namespace Content.Server.Objectives.Systems;
+
+/// <summary>
+/// Handles role requirement for objectives that require a certain (probably antagonist) role(s).
+/// </summary>
+public sealed class RoleRequirementSystem : EntitySystem
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<RoleRequirementComponent, RequirementCheckEvent>(OnCheck);
+    }
+
+    private void OnCheck(EntityUid uid, RoleRequirementComponent comp, ref RequirementCheckEvent args)
+    {
+        if (args.Cancelled)
+            return;
+
+        // this whitelist trick only works because roles are components on the mind and not entities
+        // if that gets reworked then this will need changing
+        if (!comp.Roles.IsValid(args.MindId, EntityManager))
+            args.Cancelled = true;
+    }
+}