Implement production vertical slice foundation

game/domain/rules/dive_accessibility_adjustments.gd

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+class_name DiveAccessibilityAdjustments
+extends RefCounted
+
+var oxygen_consumption_multiplier: float
+var battery_consumption_multiplier: float
+var pressure_damage_multiplier: float
+
+
+func _init(
+	p_oxygen_consumption_multiplier: float = 1.0,
+	p_battery_consumption_multiplier: float = 1.0,
+	p_pressure_damage_multiplier: float = 1.0
+) -> void:
+	oxygen_consumption_multiplier = p_oxygen_consumption_multiplier
+	battery_consumption_multiplier = p_battery_consumption_multiplier
+	pressure_damage_multiplier = p_pressure_damage_multiplier
+
+
+func validation_error() -> String:
+	for multiplier: float in [
+		oxygen_consumption_multiplier,
+		battery_consumption_multiplier,
+		pressure_damage_multiplier,
+	]:
+		if not is_finite(multiplier) or multiplier <= 0.0:
+			return "accessibility multipliers must be finite and positive"
+	return ""