Add cloud pubsub as a dependency

service/pom.xml

@@ -214,6 +214,18 @@
       <version>4.2.0</version>
     </dependency>
 
+    <dependency>
+      <groupId>com.google.cloud</groupId>
+      <artifactId>google-cloud-pubsub</artifactId>
+      <exclusions>
+        <!-- Conflicts with our direct Guava dependency -->
+        <exclusion>
+          <groupId>com.google.guava</groupId>
+          <artifactId>failureaccess</artifactId>
+        </exclusion>
+      </exclusions>
+    </dependency>
+
     <dependency>
       <groupId>com.google.firebase</groupId>
       <artifactId>firebase-admin</artifactId>