I stumbled on an error while I prepared the readme.Rmd.

Error in globalCallingHandlers(condition = global_progression_handler) : 
  should not be called with handlers on the stack

The documentation of progressr states that

Setting progression handlers is a privilege that should be left to the end user

I think we should follow that recommendation and don't try to fix that error.

We could

• keep only one option verbose and remove show_progress
• switch all progress bars to progressr and use them only if progressr is installed
• Let the user decide if progressbars should be visible (add a example using handlers(global = TRUE) to the documentation)

What do you think @e-kotov, @Nowosad ?