Upgrade notes for Shiny 1.5.0

Full changelog

Fixed #2869: Until this release, renderImage() had a dangerous default of deleteFile = TRUE. (Sorry!) Going forward, calls to renderImage() will need an explicit deleteFile argument; for now, failing to provide one will result in a warning message, and the file will be deleted if it appears to be within the tempdir(). (#2881)

The new shinyAppTemplate() function creates a new template Shiny application, where components are optional, such as helper files in an R/ subdirectory, a module, and various kinds of tests. (#2704)
runTests() is a new function that behaves much like R CMD check. runTests() invokes all of the top-level R files in the tests/ directory inside an application, in that application’s environment. (#2585)
testServer() is a new function for testing reactive behavior inside server functions and modules. (#2682, #2764, #2807)
The new moduleServer function provides a simpler interface for creating and using modules. (#2773)
Resolved #2732: markdown() is a new function for writing Markdown with Github extensions directly in Shiny UIs. Markdown rendering is performed by the commonmark package. (#2737)
The getCurrentOutputInfo() function can now return the background color (bg), foreground color (fg), accent (i.e., hyperlink) color, and font information of the output’s HTML container. This information is reported by plotOutput(), imageOutput(), and any other output bindings containing a class of .shiny-report-theme. This feature allows developers to style an output’s contents based on the container’s CSS styling. (#2740)

Fixed #2042, #2628: In a dateInput and dateRangeInput, disabled months and years are now a lighter gray, to make it easier to see that they are disabled. (#2690)
getCurrentOutputInfo() previously threw an error when called from outside of an output; now it returns NULL. (#2707 and #2858)
Added a label to observer that auto-reloads R/ directory to avoid confusion when using reactlog. (#58)
getDefaultReactiveDomain() can now be called inside a session$onSessionEnded callback and will return the calling session information. (#2757)
Added a 'function' class to reactive() and reactiveVal() objects. (#2793)
Added a new option (type = "hidden") to tabsetPanel(), making it easier to set the active tab via other input controls (e.g., radioButtons()) rather than tabs or pills. Use this option in conjunction with updateTabsetPanel() and the new tabsetPanelBody() function (see help(tabsetPanel) for an example and more details). (#2814)
Added function updateActionLink() to update an actionLink() label and/or icon value. (#2811)
Fixed #2856: Bumped jQuery 3 from 3.4.1 to 3.5.1. (#2857)

Fixed #2606: debounce() would not work properly if the code in the reactive expression threw an error on the first run. (#2652)
Fixed #2653: The dataTableOutput() could have incorrect output if certain characters were in the column names. (#2658)

Updated from Font-Awesome 5.3.1 to 5.13.0, which includes icons related to COVID-19. For upgrade notes, see https://github.com/FortAwesome/Font-Awesome/blob/master/UPGRADING.md. (#2891)