SampleJsonDataGenerator: generate GUID for uuid/guid format strings (#1895)

* Initial plan

* Add UUID/GUID format support to SampleJsonDataGenerator

Co-authored-by: lahma <[email protected]>

* Use JsonFormatStrings.Uuid constant instead of string literal "uuid"

Co-authored-by: lahma <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: lahma <[email protected]>

Author: Copilot

src/NJsonSchema.Tests/Generation/SampleJsonDataGeneratorTests.cs

@@ -452,6 +452,38 @@ public async Task PropertyWithDefaultDefiniton()
 
         //exclusiveMaximum
 
+        [Theory]
+        [InlineData("uuid")]
+        [InlineData("guid")]
+        public async Task PropertyWithGuidOrUuidFormatGeneratesGuid(string format)
+        {
+            // Arrange
+            var data = $@"{{
+                ""$schema"": ""http://json-schema.org/draft-04/schema#"",
+                ""title"": ""test schema"",
+                ""type"": ""object"",
+                ""required"": [
+                  ""identifier""
+                ],
+                ""properties"": {{
+                  ""identifier"": {{
+                    ""type"": ""string"",
+                    ""format"": ""{format}""
+                  }}
+                }}
+              }}";
+            var generator = new SampleJsonDataGenerator();
+            var schema = await JsonSchema.FromJsonAsync(data);
+
+            // Act
+            var testJson = generator.Generate(schema);
+
+            // Assert
+            var identifierValue = testJson.SelectToken("identifier")?.Value<string>();
+            Assert.NotNull(identifierValue);
+            Assert.True(System.Guid.TryParse(identifierValue, out _), $"Expected a GUID but got: {identifierValue}");
+        }
+
         [Fact]
         public async Task PropertyExclusiveMinimumDefiniton()
         {

src/NJsonSchema/Generation/SampleJsonDataGenerator.cs

@@ -174,6 +174,12 @@ private static JToken HandleStringType(JsonSchema schema, JsonSchemaProperty? pr
             {
                 return JToken.FromObject(DateTimeOffset.UtcNow.ToString("o"));
             }
+#pragma warning disable CS0618 // Type or member is obsolete
+            else if (schema.Format == JsonFormatStrings.Guid || schema.Format == JsonFormatStrings.Uuid)
+#pragma warning restore CS0618 // Type or member is obsolete
+            {
+                return JToken.FromObject(Guid.NewGuid().ToString());
+            }
             else if (property != null)
             {
                 return JToken.FromObject(property.Name);