introduce decorators for tm_g_ipp (#1263)

Part of insightsengineering/teal#1371

<details><summary> Working Example </summary>

```r

devtools::load_all("../teal")
devtools::load_all(".")

library(nestcolor)
library(dplyr)

data <- teal_data()
data <- within(data, {
  ADSL <- tmc_ex_adsl %>%
    slice(1:20) %>%
    df_explicit_na()
  ADLB <- tmc_ex_adlb %>%
    filter(USUBJID %in% ADSL$USUBJID) %>%
    df_explicit_na() %>%
    filter(AVISIT != "SCREENING")
})
join_keys(data) <- default_cdisc_join_keys[names(data)]

ADSL <- data[["ADSL"]]
ADLB <- data[["ADLB"]]

caption_decorator <- function(default_caption = "I am a good decorator", .var_to_replace = "plot") {
  teal_transform_module(
    label = "Caption",
    ui = function(id) shiny::textInput(shiny::NS(id, "footnote"), "Footnote", value = default_caption),
    server = make_teal_transform_server(
      substitute({
        .var_to_replace <- .var_to_replace + ggplot2::labs(caption = footnote)
      }, env = list(.var_to_replace = as.name(.var_to_replace)))
    )
  )
}

app <- init(
  data = data,
  modules = modules(
    tm_g_ipp(
      label = "Individual Patient Plot",
      dataname = "ADLB",
      arm_var = choices_selected(
        value_choices(ADLB, "ARMCD"),
        "ARM A"
      ),
      paramcd = choices_selected(
        value_choices(ADLB, "PARAMCD"),
        "ALT"
      ),
      aval_var = choices_selected(
        variable_choices(ADLB, c("AVAL", "CHG")),
        "AVAL"
      ),
      avalu_var = choices_selected(
        variable_choices(ADLB, c("AVALU")),
        "AVALU",
        fixed = TRUE
      ),
      id_var = choices_selected(
        variable_choices(ADLB, c("USUBJID")),
        "USUBJID",
        fixed = TRUE
      ),
      visit_var = choices_selected(
        variable_choices(ADLB, c("AVISIT")),
        "AVISIT"
      ),
      baseline_var = choices_selected(
        variable_choices(ADLB, c("BASE")),
        "BASE",
        fixed = TRUE
      ),
      add_baseline_hline = FALSE,
      separate_by_obs = FALSE,
      decorators = list(caption_decorator(.var_to_replace = "plot"))
    )
  )
)
if (interactive()) {
  shinyApp(app$ui, app$server)
}

```

</details>

R/tm_g_ipp.R

@@ -179,6 +179,15 @@ template_g_ipp <- function(dataname = "ANL",
 #'
 #' @inherit module_arguments return seealso
 #'
+#' @section Decorating `tm_g_ipp`:
+#'
+#' This module generates the following objects, which can be modified in place using decorators:
+#' - `plot` (`ggplot2`)
+#'
+#' For additional details and examples of decorators, refer to the vignette
+#' `vignette("decorate-modules-output", package = "teal")` or the [`teal_transform_module()`] documentation.
+#'
+#'
 #' @examplesShinylive
 #' library(teal.modules.clinical)
 #' interactive <- function() TRUE
@@ -293,7 +302,8 @@ tm_g_ipp <- function(label,
                      plot_width = NULL,
                      pre_output = NULL,
                      post_output = NULL,
-                     ggplot2_args = teal.widgets::ggplot2_args()) {
+                     ggplot2_args = teal.widgets::ggplot2_args(),
+                     decorators = NULL) {
   if (lifecycle::is_present(base_var)) {
     baseline_var <- base_var
     warning(
@@ -329,6 +339,8 @@ tm_g_ipp <- function(label,
   checkmate::assert_class(pre_output, classes = "shiny.tag", null.ok = TRUE)
   checkmate::assert_class(post_output, classes = "shiny.tag", null.ok = TRUE)
   checkmate::assert_class(ggplot2_args, "ggplot2_args")
+  decorators <- normalize_decorators(decorators)
+  assert_decorators(decorators, null.ok = TRUE, "plot")
 
   args <- as.list(environment())
   data_extract_list <- list(
@@ -354,7 +366,8 @@ tm_g_ipp <- function(label,
         parentname = parentname,
         plot_height = plot_height,
         plot_width = plot_width,
-        ggplot2_args = ggplot2_args
+        ggplot2_args = ggplot2_args,
+        decorators = decorators
       )
     ),
     datanames = teal.transform::get_extract_datanames(data_extract_list)
@@ -428,6 +441,7 @@ ui_g_ipp <- function(id, ...) {
         data_extract_spec = a$baseline_var,
         is_single_dataset = is_single_dataset_value
       ),
+      ui_decorate_teal_data(ns("decorator"), decorators = select_decorators(a$decorators, "plot")),
       teal.widgets::panel_group(
         teal.widgets::panel_item(
           "Additional plot settings",
@@ -479,7 +493,8 @@ srv_g_ipp <- function(id,
                       plot_height,
                       plot_width,
                       label,
-                      ggplot2_args) {
+                      ggplot2_args,
+                      decorators) {
   with_reporter <- !missing(reporter) && inherits(reporter, "Reporter")
   with_filter <- !missing(filter_panel_api) && inherits(filter_panel_api, "FilterPanelAPI")
   checkmate::assert_class(data, "reactive")
@@ -611,7 +626,13 @@ srv_g_ipp <- function(id,
     })
 
     # Outputs to render.
-    plot_r <- reactive(all_q()[["plot"]])
+    decorated_all_q <- srv_decorate_teal_data(
+      id = "decorator",
+      data = all_q,
+      decorators = select_decorators(decorators, "plot"),
+      expr = print(plot)
+    )
+    plot_r <- reactive(decorated_all_q()[["plot"]])
 
     # Insert the plot into a plot with settings module from teal.widgets
     pws <- teal.widgets::plot_with_settings_srv(
@@ -623,7 +644,7 @@ srv_g_ipp <- function(id,
 
     teal.widgets::verbatim_popup_srv(
       id = "rcode",
-      verbatim_content = reactive(teal.code::get_code(all_q())),
+      verbatim_content = reactive(teal.code::get_code(req(decorated_all_q()))),
       title = label
     )
 
@@ -642,7 +663,7 @@ srv_g_ipp <- function(id,
           card$append_text("Comment", "header3")
           card$append_text(comment)
         }
-        card$append_src(teal.code::get_code(all_q()))
+        card$append_src(teal.code::get_code(req(decorated_all_q())))
         card
       }
       teal.reporter::simple_reporter_srv("simple_reporter", reporter = reporter, card_fun = card_fun)