Assess id argument in init()

[donyunardi]

Summary

We need to evaluate whether the id argument is still necessary given recent improvements to make teal a modular framework:

• Remove insertUI in the teal::init #669
• Follow up on implementing teal as a module nestdevs-tasks#62

As noted in the documentation, the id argument is currently a legacy feature:

teal/R/init.R

Lines 31 to 33 in 997da60

	#' @param id (`character`) Optionally,
	#' a string specifying the `shiny` module id in cases it is used as a `shiny` module
	#' rather than a standalone `shiny` app. This is a legacy feature.

Acceptance Criteria

• Assess whether the id argument should be retained or removed.
• If removal is needed, initiate the soft-deprecation process.
• Update the documentation (roxygen and vignette) to reflect any changes.

[gogonzo]

id argument is not needed anymore since introduction of ui/srv_teal in #669. Instead of id in teal::init one can call modules directly instead of indirectly set id.

[m7pr]

CC @donyunardi