The feature of messaging between the users


My name is Kate, I’m a PM in Halo lab, we’re development agency that builds JAMStack application.
One of our clients uses strapi’s free plan to manage data on their website: this company provides users with a digitalized list of books from their collections (libraries).
At the moment strapi manages users’ authentication and books collections

Right now we need to implement the feature of messaging between the users, but we can’t find any relevant information in your documentation.

Please help me to figure out a few things:
do you have some pre-built plugin that allows users to send messages to each other? if so is it payed or free?
if you don’t have relevant plugins, do you any guides of how we can implement it within strapi by ourselves?
please also let me know if there is no way to implement it within strapi CMS and we should look for a standalone solution

Looking forward to hearing from you.
Thank you for your attention.