Create a custom field, this field must communicate with an external or internal database, when the user registers in moodle, ask for a code if he is in this base he lets register, otherwise he does not let create a user. Thank you for your help
If you want it specifically this way, pretty sure you are going to be looking at a plugin - you might search the plugin database to see if there is something there that will work - otherwise, you will need to create it yourself...however external database should allow you to only let certain user create an account - easiest to limit them by group - can you do something like that? I know that with ldap, I only let users login if they are a member of a certain group and that works well.
I'm reading the documentation, I'm going to create a plugin, I think it's the best alternative.
Thank you for your help!
Thank you for your help!