Missing docs in kafka and vertx implementation (#183)

Signed-off-by: Francesco Guardiani <francescoguard@gmail.com>

Author: slinkydeveloper

http/vertx/pom.xml

@@ -37,6 +37,13 @@
     </properties>
 
     <dependencies>
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>jsr305</artifactId>
+            <version>3.0.2</version>
+            <scope>provided</scope>
+            <optional>true</optional>
+        </dependency>
         <dependency>
             <groupId>io.cloudevents</groupId>
             <artifactId>cloudevents-core</artifactId>

http/vertx/src/main/java/io/cloudevents/http/vertx/VertxMessageFactory.java

@@ -14,12 +14,14 @@
 import io.vertx.core.buffer.Buffer;
 import io.vertx.core.http.*;
 
+import javax.annotation.ParametersAreNonnullByDefault;
 import java.util.function.Consumer;
 
 /**
  * This class provides a collection of methods to create {@link io.cloudevents.core.message.MessageReader}
  * and {@link io.cloudevents.core.message.MessageWriter} for Vert.x HTTP Client and Server.
  */
+@ParametersAreNonnullByDefault
 public final class VertxMessageFactory {
 
     private VertxMessageFactory() {

kafka/pom.xml

@@ -36,6 +36,13 @@
     </properties>
 
     <dependencies>
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>jsr305</artifactId>
+            <version>3.0.2</version>
+            <scope>provided</scope>
+            <optional>true</optional>
+        </dependency>
         <dependency>
             <groupId>io.cloudevents</groupId>
             <artifactId>cloudevents-core</artifactId>

kafka/src/main/java/io/cloudevents/kafka/KafkaMessageFactory.java

@@ -30,10 +30,13 @@
 import org.apache.kafka.clients.producer.ProducerRecord;
 import org.apache.kafka.common.header.Headers;
 
+import javax.annotation.ParametersAreNonnullByDefault;
+
 /**
  * This class provides a collection of methods to create {@link io.cloudevents.core.message.MessageReader}
  * and {@link io.cloudevents.core.message.MessageWriter} for Kafka Producer and Consumer.
  */
+@ParametersAreNonnullByDefault
 public final class KafkaMessageFactory {
 
     private KafkaMessageFactory() {