Fire stacks trigger (#39530)

* Simple as

* whoops

* not gonna work

* chopped

* missed something

* Better name

* formatting

---------

Co-authored-by: iaada <iaada@users.noreply.github.com>
Co-authored-by: slarticodefast <161409025+slarticodefast@users.noreply.github.com>

Content.Server/Trigger/Systems/FlameStackOnTriggerSystem.cs

@@ -0,0 +1,37 @@
+using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Trigger;
+using Content.Shared.Trigger.Components.Effects;
+
+namespace Content.Server.Trigger.Systems;
+
+/// <summary>
+/// Trigger system for setting something on fire.
+/// </summary>
+/// <seealso cref="IgniteOnTriggerSystem"/>
+public sealed class FlameStackOnTriggerSystem : EntitySystem
+{
+    [Dependency] private readonly FlammableSystem _flame = default!;
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<FlameStackOnTriggerComponent, TriggerEvent>(OnTrigger);
+    }
+
+    private void OnTrigger(Entity<FlameStackOnTriggerComponent> ent, ref TriggerEvent args)
+    {
+        if (args.Key != null && !ent.Comp.KeysIn.Contains(args.Key))
+            return;
+
+        var target = ent.Comp.TargetUser ? args.User : ent.Owner;
+
+        if (target == null)
+            return;
+
+        _flame.AdjustFireStacks(target.Value, ent.Comp.FireStacks, ignite: ent.Comp.DoIgnite);
+
+        args.Handled = true;
+    }
+}