fix(scala): rename local var to avoid named arg shadowing in Scala 3.8.2

Scala 3.8.2 resolves 'additionalProperties = ...' inside copy() to
the local variable instead of the named parameter, causing type mismatch
errors. Rename the local variable from 'additionalProperties' to
'extraProperties' and use dot notation for copy() calls.

Author: Fluf22

templates/scala/serializer.mustache

@@ -26,12 +26,12 @@ class {{classname}}Serializer extends Serializer[{{classname}}] {
 
         {{#additionalProperties.isAnyType}}
         val fields = Set({{#vars}}"{{#vendorExtensions.x-unescaped-name}}{{{.}}}{{/vendorExtensions.x-unescaped-name}}{{^vendorExtensions.x-unescaped-name}}{{{name}}}{{/vendorExtensions.x-unescaped-name}}"{{^-last}}, {{/-last}}{{/vars}})
-        val additionalProperties = jobject removeField {
+        val extraProperties = jobject removeField {
           case (name, _) if fields.contains(name) => true
           case _                                  => false
         }
-        additionalProperties match {
-          case JObject(fieldsList) => obj copy (additionalProperties = Some(fieldsList))
+        extraProperties match {
+          case JObject(fieldsList) => obj.copy(additionalProperties = Some(fieldsList))
           case _                   => obj
         }
         {{/additionalProperties.isAnyType}}