expedition air mod (#17369)

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

Content.Shared/Salvage/Expeditions/Modifiers/SalvageAirMod.cs

@@ -0,0 +1,43 @@
+using Content.Shared.Atmos;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype.List;
+
+namespace Content.Shared.Salvage.Expeditions.Modifiers;
+
+/// <summary>
+/// Prototype for a planet's air gas mixture.
+/// Used when creating the planet for a salvage expedition.
+/// Which one is selected depends on the mission difficulty, different weightedRandoms are picked from.
+/// </summary>
+[Prototype("salvageAirMod")]
+public sealed class SalvageAirMod : IPrototype, ISalvageMod
+{
+    [IdDataField]
+    public string ID { get; } = default!;
+
+    /// <inheritdoc/>
+    [DataField("desc")]
+    public string Description { get; } = string.Empty;
+
+    /// <inheritdoc/>
+    [DataField("cost")]
+    public float Cost { get; } = 0f;
+
+    /// <summary>
+    /// Set to true if this planet will have no atmosphere.
+    /// </summary>
+    [DataField("space")]
+    public bool Space;
+
+    /// <summary>
+    /// Number of moles of each gas in the mixture.
+    /// </summary>
+    [DataField("gases")]
+    public float[] Gases = new float[Atmospherics.AdjustedNumberOfGases];
+
+    /// <summary>
+    /// Biomes this air mixture is allowed to occur in.
+    /// </summary>
+    [DataField("biomes", customTypeSerializer: typeof(PrototypeIdListSerializer<SalvageBiomeMod>))]
+    public List<string>? Biomes;
+}