Remove the use of javax.annotation.Nullable.

It's only used for AutoValue, which is perfectly happy with a locally-defined @nullable annotation. Without this change, a clean Maven build fails, because we were previously getting javax.annotation.Nullable through an indirect dependency which was removed.

PiperOrigin-RevId: 293256408

Author: eamonnmcmanus

invoker/core/pom.xml

@@ -52,11 +52,6 @@
       <artifactId>cloudevents-api</artifactId>
       <version>1.2.0</version>
     </dependency>
-    <dependency>
-      <groupId>javax.annotation</groupId>
-      <artifactId>javax.annotation-api</artifactId>
-      <version>1.3.2</version>
-    </dependency>
     <dependency>
       <groupId>com.google.code.gson</groupId>
       <artifactId>gson</artifactId>

invoker/core/src/main/java/com/google/cloud/functions/invoker/CloudFunctionsContext.java

@@ -4,11 +4,16 @@
 import com.google.cloud.functions.Context;
 import com.google.gson.Gson;
 import com.google.gson.TypeAdapter;
-import javax.annotation.Nullable;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 
 /** Event context (metadata) for events handled by Cloud Functions. */
 @AutoValue
 abstract class CloudFunctionsContext implements Context {
+  // AutoValue recognizes any annotation called @Nullable, so no need to import this from anywhere.
+  @Retention(RetentionPolicy.SOURCE)
+  @interface Nullable {}
+
   @Nullable
   public abstract String eventId();