This is the server-side function for creating a dynamic dropdown menu.
renderDropdownMenu(expr, env = parent.frame(), quoted = FALSE)An expression that returns a Shiny tag object, HTML(),
or a list of such objects.
The parent environment for the reactive expression. By default,
this is the calling environment, the same as when defining an ordinary
non-reactive expression. If expr is a quosure and quoted is TRUE,
then env is ignored.
If it is TRUE, then the quote()ed value of expr
will be used when expr is evaluated. If expr is a quosure and you
would like to use its expression as a value for expr, then you must set
quoted to TRUE.