Adds a UI for gas mixers (#5165)

Co-authored-by: E F R <602406+Efruit@users.noreply.github.com>
Co-authored-by: Paul Ritter <ritter.paul1@googlemail.com>
Co-authored-by: ike709 <ike709@github.com>

Content.Shared/Atmos/Piping/Trinary/Components/SharedGasMixerComponent.cs

@@ -0,0 +1,63 @@
+using System;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Atmos.Piping.Trinary.Components
+{
+    [Serializable, NetSerializable]
+    public enum GasMixerUiKey
+    {
+        Key,
+    }
+
+    [Serializable, NetSerializable]
+    public class GasMixerBoundUserInterfaceState : BoundUserInterfaceState
+    {
+        public string MixerLabel { get; }
+        public float OutputPressure { get; }
+        public bool Enabled { get; }
+
+        public float NodeOne { get; }
+
+        public GasMixerBoundUserInterfaceState(string mixerLabel, float outputPressure, bool enabled, float nodeOne)
+        {
+            MixerLabel = mixerLabel;
+            OutputPressure = outputPressure;
+            Enabled = enabled;
+            NodeOne = nodeOne;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public class GasMixerToggleStatusMessage : BoundUserInterfaceMessage
+    {
+        public bool Enabled { get; }
+
+        public GasMixerToggleStatusMessage(bool enabled)
+        {
+            Enabled = enabled;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public class GasMixerChangeOutputPressureMessage : BoundUserInterfaceMessage
+    {
+        public float Pressure { get; }
+
+        public GasMixerChangeOutputPressureMessage(float pressure)
+        {
+            Pressure = pressure;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public class GasMixerChangeNodePercentageMessage : BoundUserInterfaceMessage
+    {
+        public float NodeOne { get; }
+
+        public GasMixerChangeNodePercentageMessage(float nodeOne)
+        {
+            NodeOne = nodeOne;
+        }
+    }
+}