creation token rest post via postman Access Denied
I eventually figure out what the problem was after many many attempts.

There was actually an issue with postman access to Drupal, it's because Drupal was configured in services.yml to allow access only to Angular API (for my project) by:

Configure requests allowed from specific origins.

allowedOrigins: ['http://localhost:4200']

I changed it to test with postman by:

Configure requests allowed from specific origins.

allowedOrigins: ['*']

Consequently, my token was created in postman with post method which means: bye to 403 error!!!

Hope that can help someone :)

Thank you!