[online] Honor generator environment variable and system property (Op…

…enAPITools#3265)

Previously, this pulled from the GENERATOR_HOST system property. This
should have been an environment variable. Fallback is now generator.host
system property.

modules/openapi-generator-online/src/main/java/org/openapitools/codegen/online/configuration/OpenAPIDocumentationConfig.java

@@ -68,7 +68,11 @@ ApiInfo apiInfo() {
     public Docket customImplementation(){
         String host;
         try {
-            host = new URI(System.getProperty("GENERATOR_HOST", "http://localhost")).getHost();
+            String baseUrl = System.getenv("GENERATOR_HOST");
+            if (baseUrl == null) {
+                baseUrl = System.getProperty("generator.host", "http://localhost");
+            }
+            host = new URI(baseUrl).getHost();
         } catch (URISyntaxException e) {
             host = "";
         }