Change ReplacePlaceholders to return NULL for unresolved

Previously, ReplacePlaceholders threw PlaceholderResolutionException when a placeholder could not be resolved. Now, unresolved placeholders are replaced with "NULL" instead. All exception references and related tests have been updated to reflect this new behavior. Documentation has also been revised accordingly.

tests/ReC.Tests/Application/Behaviors/InvokeActionTests.cs

@@ -1,6 +1,5 @@
 using System.ComponentModel.DataAnnotations.Schema;
 using ReC.Application.Common.Dto;
-using ReC.Application.Common.Exceptions;
 
 namespace ReC.Tests.Application.Behaviors;
 
@@ -211,46 +210,40 @@ public class InvokeActionTests
     #region ReplacePlaceholders - Exception Tests
 
     [Test]
-    public void ReplacePlaceholders_UnresolvableColumn_ThrowsPlaceholderResolutionException()
+    public void ReplacePlaceholders_UnresolvableColumn_ReturnsNull()
     {
         var input = "WHERE X = {#INT#NON_EXISTING}";
 
-        var ex = Assert.Throws<PlaceholderResolutionException>(() =>
-            input.ReplacePlaceholders(_foo, _bar, _fuz));
-
-        Assert.That(ex!.ColumnName, Is.EqualTo("NON_EXISTING"));
-        Assert.That(ex.Placeholder, Is.EqualTo("{#INT#NON_EXISTING}"));
-        Assert.That(ex.Input, Is.EqualTo(input));
+        var result = input.ReplacePlaceholders(_foo, _bar, _fuz);
+        Assert.That(result, Is.EqualTo("WHERE X = NULL"));
     }
 
     [Test]
-    public void ReplacePlaceholders_NoObjectsProvided_ThrowsPlaceholderResolutionException()
+    public void ReplacePlaceholders_NoObjectsProvided_ReturnsNull()
     {
         var input = "WHERE X = {#INT#BAZ}";
 
-        Assert.Throws<PlaceholderResolutionException>(() =>
-            input.ReplacePlaceholders());
+        var result = input.ReplacePlaceholders();
+        Assert.That(result, Is.EqualTo("WHERE X = NULL"));
     }
 
     [Test]
-    public void ReplacePlaceholders_ObjectWithoutColumnAttributes_ThrowsPlaceholderResolutionException()
+    public void ReplacePlaceholders_ObjectWithoutColumnAttributes_ReturnsNull()
     {
         var model = new NoColumnModel { Id = 1, Name = "Test" };
         var input = "WHERE X = {#INT#Id}";
 
-        Assert.Throws<PlaceholderResolutionException>(() =>
-            input.ReplacePlaceholders(model));
+        var result = input.ReplacePlaceholders(model);
+        Assert.That(result, Is.EqualTo("WHERE X = NULL"));
     }
 
     [Test]
-    public void ReplacePlaceholders_MixedResolvableAndUnresolvable_ThrowsOnUnresolvable()
+    public void ReplacePlaceholders_MixedResolvableAndUnresolvable_ReturnsNullForUnresolvable()
     {
         var input = "WHERE BAZ = {#INT#BAZ} AND X = {#INT#UNKNOWN}";
 
-        var ex = Assert.Throws<PlaceholderResolutionException>(() =>
-            input.ReplacePlaceholders(_foo, _bar, _fuz));
-
-        Assert.That(ex!.ColumnName, Is.EqualTo("UNKNOWN"));
+        var result = input.ReplacePlaceholders(_foo, _bar, _fuz);
+        Assert.That(result, Is.EqualTo("WHERE BAZ = 2 AND X = NULL"));
     }
 
     #endregion