Update Checkstyle to https Apache 2 License

Issue gh-1370

build.gradle

@@ -34,5 +34,10 @@ gradle.taskGraph.whenReady { graph ->
 				jacoco.enabled = jacocoEnabled
 			}
 		}
+		plugins.withType(CheckstylePlugin) {
+			dependencies {
+				checkstyle files("$rootDir/etc/checkstyle/src/main/resources")
+			}
+		}
 	}
 }

etc/checkstyle/checkstyle.xml

@@ -8,5 +8,8 @@
 	</module>
 
 	<!-- Root Checks -->
-	<module name="io.spring.javaformat.checkstyle.SpringChecks"/>
+	<module name="io.spring.javaformat.checkstyle.check.SpringHeaderCheck">
+		<property name="headerType" value="https-apache2"/>
+	</module>
+
 </module>

etc/checkstyle/src/main/resources/io/spring/javaformat/checkstyle/check/header-https-apache2.txt

@@ -0,0 +1,15 @@
+/*
+ * Copyright ${copyright-pattern} the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */