allow overwriting the port binding via environment variables (#37)

Author: Madh93

src/main/java/cloud/localstack/docker/annotation/LocalstackDockerAnnotationProcessor.java

@@ -36,12 +36,16 @@ private LocalstackDockerConfiguration processDockerPropertiesAnnotation(Localsta
             .ignoreDockerRunErrors(properties.ignoreDockerRunErrors())
             .randomizePorts(properties.randomizePorts())
             .imageTag(StringUtils.isEmpty(properties.imageTag()) ? null : properties.imageTag())
-            .portEdge(properties.portEdge())
-            .portElasticSearch(properties.portElasticSearch())
+            .portEdge(getEnvOrDefault("LOCALSTACK_EDGE_PORT", properties.portEdge()))
+            .portElasticSearch(getEnvOrDefault("LOCALSTACK_ELASTICSEARCH_PORT", properties.portElasticSearch()))
             .useSingleDockerContainer(properties.useSingleDockerContainer())
             .build();
     }
 
+    private String getEnvOrDefault(final String environmentVariable, final String defaultValue) {
+        return System.getenv().getOrDefault(environmentVariable, defaultValue);
+    }
+
     private Map<Integer, Integer> getCustomPortMappings(final LocalstackDockerProperties properties) {
         final Map<Integer, Integer> portMappings = new HashMap<>();
         for (String service : properties.services()) {

src/main/java/cloud/localstack/docker/annotation/LocalstackDockerProperties.java

@@ -52,12 +52,14 @@
     String imageTag() default "";
 
     /**
-     * Port number for the edge service, the main entry point for all API invocations
+     * Port number for the edge service, the main entry point for all API invocations. Alternatively, use the
+     * LOCALSTACK_EDGE_PORT environment variable.
      */
     String portEdge() default "4566";
 
     /**
-     * Port number for the elasticsearch service
+     * Port number for the elasticsearch service. Alternatively, use the LOCALSTACK_ELASTICSEARCH_PORT environment
+     * variable.
      */
     String portElasticSearch() default "4571";