feat(auditlog): add AuditLog:InboundMaxBytes option (default 1 MiB, [8 KiB, 16 MiB])

tests/ScadaLink.AuditLog.Tests/Configuration/AuditLogOptionsBindingTests.cs

@@ -45,7 +45,8 @@ public class AuditLogOptionsBindingTests
                     "RedactSqlParamsMatching": "@token|@secret"
                   }
                 },
-                "RetentionDays": 180
+                "RetentionDays": 180,
+                "InboundMaxBytes": 524288
               }
             }
             """;
@@ -64,6 +65,7 @@ public class AuditLogOptionsBindingTests
         Assert.Equal(4096, opts.DefaultCapBytes);
         Assert.Equal(32768, opts.ErrorCapBytes);
         Assert.Equal(180, opts.RetentionDays);
+        Assert.Equal(524_288, opts.InboundMaxBytes);
 
         // HeaderRedactList: the Microsoft.Extensions.Configuration list binder
         // APPENDS to the default list, so we assert containment rather than

tests/ScadaLink.AuditLog.Tests/Configuration/AuditLogOptionsValidatorTests.cs

@@ -0,0 +1,53 @@
+using ScadaLink.AuditLog.Configuration;
+
+namespace ScadaLink.AuditLog.Tests.Configuration;
+
+/// <summary>
+/// Task 1 of <c>docs/plans/2026-05-23-inbound-api-full-response-audit.md</c>:
+/// pins the <see cref="AuditLogOptions.InboundMaxBytes"/> default to 1 MiB and
+/// the validator bounds to <c>[8 KiB, 16 MiB]</c>. The inbound channel needs a
+/// much larger ceiling than the 8 KiB / 64 KiB default/error caps that other
+/// channels use, but unbounded would let any caller flood the central
+/// <c>AuditLog</c> table with arbitrarily large bodies — hence the upper bound.
+/// Companion to <see cref="AuditLogOptionsTests"/> which covers the existing
+/// cap-bytes + retention invariants.
+/// </summary>
+public class AuditLogOptionsValidatorTests
+{
+    [Fact]
+    public void Validate_InboundMaxBytes_DefaultOptions_IsOneMebibyte()
+    {
+        // The doc'd default per docs/plans/2026-05-23-inbound-api-full-response-audit-design.md
+        // is 1 048 576 bytes (1 MiB). Pin it so a config drift is a test failure,
+        // not a silent operational surprise.
+        var opts = new AuditLogOptions();
+        Assert.Equal(1_048_576, opts.InboundMaxBytes);
+    }
+
+    [Theory]
+    [InlineData(8_192)]              // documented min
+    [InlineData(1_048_576)]          // default
+    [InlineData(16_777_216)]         // documented max
+    public void Validate_InboundMaxBytes_InRange_Passes(int value)
+    {
+        var validator = new AuditLogOptionsValidator();
+        var opts = new AuditLogOptions { InboundMaxBytes = value };
+        Assert.True(validator.Validate(null, opts).Succeeded);
+    }
+
+    [Theory]
+    [InlineData(0)]
+    [InlineData(8_191)]
+    [InlineData(16_777_217)]
+    [InlineData(int.MaxValue)]
+    public void Validate_InboundMaxBytes_OutOfRange_Fails(int value)
+    {
+        var validator = new AuditLogOptionsValidator();
+        var opts = new AuditLogOptions { InboundMaxBytes = value };
+        var result = validator.Validate(null, opts);
+        Assert.False(result.Succeeded);
+        Assert.Contains(
+            result.Failures!,
+            f => f.Contains(nameof(AuditLogOptions.InboundMaxBytes), StringComparison.Ordinal));
+    }
+}