Add test for incompatible ID value.

By default, this produces:
```
The JSON value could not be converted to JsonApiDotNetCore.Serialization.Objects.SingleOrManyData`1[JsonApiDotNetCore.Serialization.Objects.ResourceObject]. Path: $.data | LineNumber: 3 | BytePositionInLine: 11.
```
which is totally unhelpful. Because this is so likely to hit users, we special-case here to produce a better error.

Author: Bart Koelman

src/JsonApiDotNetCore/Serialization/JsonConverters/ResourceObjectConverter.cs

@@ -68,6 +68,14 @@ public override ResourceObject Read(ref Utf8JsonReader reader, Type typeToConver
                         {
                             case "id":
                             {
+                                if (reader.TokenType != JsonTokenType.String)
+                                {
+                                    // Newtonsoft.Json used to auto-convert number to strings, while System.Text.Json does not. This is so likely
+                                    // to hit users during upgrade that we special-case for this and produce a helpful error message.
+                                    var jsonElement = JsonConverterSupport.ReadSubTree<JsonElement>(ref reader, options);
+                                    throw new JsonException($"Failed to convert ID '{jsonElement}' of type '{jsonElement.ValueKind}' to type 'String'.");
+                                }
+
                                 resourceObject.Id = reader.GetString();
                                 break;
                             }

test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateResourceTests.cs

@@ -958,6 +958,46 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             error.Detail.Should().StartWith("Resource ID is read-only. - Request body: <<");
         }
 
+        [Fact]
+        public async Task Cannot_update_resource_with_incompatible_ID_value()
+        {
+            // Arrange
+            WorkItem existingWorkItem = _fakers.WorkItem.Generate();
+
+            await _testContext.RunOnDatabaseAsync(async dbContext =>
+            {
+                dbContext.WorkItems.Add(existingWorkItem);
+                await dbContext.SaveChangesAsync();
+            });
+
+            var requestBody = new
+            {
+                data = new
+                {
+                    type = "workItems",
+                    id = existingWorkItem.Id,
+                    attributes = new
+                    {
+                    }
+                }
+            };
+
+            string route = $"/workItems/{existingWorkItem.StringId}";
+
+            // Act
+            (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+            // Assert
+            httpResponse.Should().HaveStatusCode(HttpStatusCode.UnprocessableEntity);
+
+            responseDocument.Errors.Should().HaveCount(1);
+
+            ErrorObject error = responseDocument.Errors[0];
+            error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+            error.Title.Should().Be("Failed to deserialize request body.");
+            error.Detail.Should().StartWith($"Failed to convert ID '{existingWorkItem.Id}' of type 'Number' to type 'String'. - Request body: <<");
+        }
+
         [Fact]
         public async Task Cannot_update_resource_with_incompatible_attribute_value()
         {