Fix and improve documentation about topic-partition initialization in the kafka dev service

Fix #45892

Author: cescoffier

docs/src/main/asciidoc/kafka-dev-services.adoc

@@ -89,8 +89,14 @@ quarkus.kafka.devservices.image-name=quay.io/strimzi-test-container/test-contain
 
 You can configure the Dev Services for Kafka to create topics once the broker is started.
 Topics are created with given number of partitions and 1 replica.
+The syntax is the following:
 
-The following example creates a topic named `test` with 3 partitions, and a second topic named `messages` with 2 partitions.
+[source, properties]
+----
+quarkus.kafka.devservices.topic-partitions.<topic-name>=<number-of-partitions>
+----
+
+The following example creates a topic named `test` with three partitions, and a second topic named `messages` with two partitions.
 
 [source, properties]
 ----

extensions/kafka-client/deployment/src/main/java/io/quarkus/kafka/client/deployment/KafkaDevServicesBuildTimeConfig.java

@@ -96,7 +96,7 @@ public String getDefaultImageName() {
     /**
      * The topic-partition pairs to create in the Dev Services Kafka broker.
      * After the broker is started, given topics with partitions are created, skipping already existing topics.
-     * For example, <code>quarkus.kafka.devservices.topic-partitions.test=2</code> will create a topic named
+     * For example, <code>quarkus.kafka.devservices.topic-partitions.my-topic=2</code> will create a topic named
      * {@code test} with 2 partitions.
      * <p>
      * The topic creation will not try to re-partition existing topics with different number of partitions.