According to the spec, extension identifier should be extensionId, not (#207)

extensionid like in the deserializer

Signed-off-by: Francisco Javier Tirado Sarti <ftirados@redhat.com>

Author: fjtirado

api/src/main/java/io/serverlessworkflow/api/deserializers/ExtensionDeserializer.java

@@ -57,7 +57,7 @@ public Extension deserialize(JsonParser jp, DeserializationContext ctxt) throws
     ObjectMapper mapper = (ObjectMapper) jp.getCodec();
     JsonNode node = jp.getCodec().readTree(jp);
 
-    String extensionId = node.get("extensionid").asText();
+    String extensionId = node.get("extensionId").asText();
 
     if (context != null) {
       try {