If key is missing, it'll be created, otherwise ignored or overwritten.
add_to_session(
session,
key = "rave_id",
val = paste(sample(c(letters, LETTERS, 0:9), 20), collapse = ""),
override = FALSE
)
If session is shiny session, returns current value stored in
session, otherwise returns NULL
'Shiny' session
character, key to store
value to store
if key exists, whether to overwrite its value