Add copyright headers to some files that don't have 'em (#9363)

I'm using 'OkHttp Authors' going forward as Square, Inc. is no longer
involved in this project.

Author: swankjesse

build-logic/src/main/kotlin/okhttp3/buildsupport/OkHttpBuildUtils.kt

@@ -1,3 +1,18 @@
+/*
+ * Copyright (c) 2026 OkHttp 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
+ *
+ *      http://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.
+ */
 package okhttp3.buildsupport
 
 import org.gradle.api.Project

okhttp/src/jvmTest/kotlin/okhttp3/InterceptorOverridesTest.kt

@@ -1,3 +1,18 @@
+/*
+ * Copyright (c) 2025 OkHttp 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
+ *
+ *      http://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.
+ */
 package okhttp3
 
 import app.cash.burst.Burst

samples/static-server/src/main/java/okhttp3/sample/SampleServer.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright (C) 2015 Square, Inc.
+ *
+ * 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
+ *
+ *      http://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.
+ */
 package okhttp3.sample;
 
 import java.io.File;