The scripting language

source

TLDR: use main language of the project to write scripts.
+1 +2 :)

Additional couple of remarks:

  1. at some moment you can think about writing tests;
  2. at some moment you need to reuse something else from the project (also it’s possible to duplicate\reimplement something from the project using scripting language);
  3. at some moment you can think about integrating functionality implemented inside the script to the main project (admin endpoint\UI\background job\etc).

That’s why it’s better to write additional logic not using a script but using the main language from the very beginning.