refactor: Fix unused member variable inspection issue

src/Recyclarr.TrashLib.Tests/Config/EnvironmentVariables/EnvironmentVariableNotDefinedExceptionTest.cs

@@ -0,0 +1,18 @@
+using FluentAssertions;
+using NUnit.Framework;
+using Recyclarr.TrashLib.Config.EnvironmentVariables;
+
+namespace Recyclarr.TrashLib.Tests.Config.EnvironmentVariables;
+
+[TestFixture]
+[Parallelizable(ParallelScope.All)]
+public class EnvironmentVariableNotDefinedExceptionTest
+{
+    [Test]
+    public void Properties_get_initialized()
+    {
+        var sut = new EnvironmentVariableNotDefinedException(15, "key");
+        sut.Line.Should().Be(15);
+        sut.EnvironmentVariableName.Should().Be("key");
+    }
+}

src/Recyclarr.TrashLib/Config/EnvironmentVariables/EnvironmentVariableNotDefinedException.cs

@@ -5,11 +5,10 @@ public class EnvironmentVariableNotDefinedException : Exception
     public int Line { get; }
     public string EnvironmentVariableName { get; }
 
-    public EnvironmentVariableNotDefinedException(int line, string environmentVariableName)
-        : base(
-            $"Line {line} refers to undefined environment variable {environmentVariableName} and no default is specified.")
+    public EnvironmentVariableNotDefinedException(int line, string envVarName)
+        : base($"Line {line} refers to undefined environment variable {envVarName} and no default is specified.")
     {
         Line = line;
-        EnvironmentVariableName = environmentVariableName;
+        EnvironmentVariableName = envVarName;
     }
 }