Fix war kotlin project

This commit fixes the generation of a web-based project using Kotlin by
propertly detecting the `ServletInitializer` template.

Closes gh-217

initializr-generator/src/main/groovy/io/spring/initializr/generator/ProjectGenerator.groovy

@@ -132,7 +132,7 @@ class ProjectGenerator {
 		write(new File(src, "${applicationName}.${extension}"), "Application.$extension", model)
 
 		if (request.packaging == 'war') {
-			def fileName = "ServletInitializer.$language"
+			def fileName = "ServletInitializer.$extension"
 			write(new File(src, fileName), fileName, model)
 		}
 

initializr-generator/src/test/groovy/io/spring/initializr/generator/ProjectGeneratorTests.groovy

@@ -554,6 +554,14 @@ class ProjectGeneratorTests {
 				.hasDependenciesCount(3)
 	}
 
+	@Test
+	void kotlinWar() {
+		def request = createProjectRequest('web')
+		request.language = 'kotlin'
+		request.packaging = 'war'
+		generateProject(request).isKotlinWarProject()
+	}
+
 	@Test
 	void invalidType() {
 		def request = createProjectRequest('web')

initializr-generator/src/test/groovy/io/spring/initializr/test/generator/ProjectAssert.groovy

@@ -130,15 +130,29 @@ class ProjectAssert {
 	}
 
 	ProjectAssert isJavaWarProject(String expectedApplicationName) {
-		isJavaProject(DEFAULT_PACKAGE_NAME, expectedApplicationName)
+		isGenericWarProject(DEFAULT_PACKAGE_NAME, expectedApplicationName, 'java', 'java')
-				.hasStaticAndTemplatesResources(true)
-				.hasFile('src/main/java/com/example/ServletInitializer.java')
 	}
 
 	ProjectAssert isJavaWarProject() {
 		isJavaWarProject(DEFAULT_APPLICATION_NAME)
 	}
 
+	ProjectAssert isGroovyWarProject() {
+		isGenericWarProject(DEFAULT_PACKAGE_NAME, DEFAULT_APPLICATION_NAME, 'groovy', 'groovy')
+	}
+
+	ProjectAssert isKotlinWarProject() {
+		isGenericWarProject(DEFAULT_PACKAGE_NAME, DEFAULT_APPLICATION_NAME, 'kotlin', 'kt')
+	}
+
+	ProjectAssert isGenericWarProject(String expectedPackageName, String expectedApplicationName,
+									  String codeLocation, String extension) {
+		String packageName = expectedPackageName.replace('.', '/')
+		isGenericProject(expectedPackageName, expectedApplicationName, codeLocation, extension)
+				.hasStaticAndTemplatesResources(true)
+				.hasFile("src/main/$codeLocation/$packageName/ServletInitializer.$extension")
+	}
+
 	ProjectAssert hasStaticAndTemplatesResources(boolean web) {
 		assertFile('src/main/resources/templates', web)
 		assertFile('src/main/resources/static', web)