Fix multipart requests for container types (webclient)

Author: sermler

modules/openapi-generator/src/main/resources/Java/libraries/webclient/api.mustache

@@ -149,7 +149,7 @@ public class {{classname}} {
 
         {{#formParams}}
         if ({{paramName}} != null)
-            formParams.add{{#collectionFormat}}All{{/collectionFormat}}("{{baseName}}", {{#isFile}}{{^collectionFormat}}{{#useAbstractionForFiles}}{{paramName}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}new FileSystemResource({{paramName}}){{/useAbstractionForFiles}}{{/collectionFormat}}{{/isFile}}{{#isFile}}{{#collectionFormat}}{{paramName}}.stream(){{^useAbstractionForFiles}}.map(FileSystemResource::new){{/useAbstractionForFiles}}.collect(Collectors.toList()){{/collectionFormat}}{{/isFile}}{{^isFile}}{{paramName}}{{/isFile}});
+            formParams.add{{#isArray}}All{{/isArray}}("{{baseName}}", {{#isFile}}{{^collectionFormat}}{{#useAbstractionForFiles}}{{paramName}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}new FileSystemResource({{paramName}}){{/useAbstractionForFiles}}{{/collectionFormat}}{{/isFile}}{{#isFile}}{{#collectionFormat}}{{paramName}}.stream(){{^useAbstractionForFiles}}.map(FileSystemResource::new){{/useAbstractionForFiles}}.collect(Collectors.toList()){{/collectionFormat}}{{/isFile}}{{^isFile}}{{paramName}}{{/isFile}});
         {{/formParams}}
         {{/hasFormParams}}