Create own Google Translate API call

Question

I try to call the Google Translate API but always get a 403 error that I didn't provide a valid API key.

I did create one, though, on my Google Cloud Platforms website here: https://console.cloud.google.com/apis/credentials

Here's what I'm doing:

library(jsonlite)
library(httr)

my_text <- c("Hallo Mama", "Ja älskar dig")
my_key <- "MYKEY"

textbody <- toJSON(list(q = my_text,
                        target = "en"))

translated <- POST(url = paste0("https://translation.googleapis.com/language/translate/v2"),
                   add_headers("key" = my_key),
                   content_type("application/json"),
                   body = textbody,
                   encode = "json")

But this returns said 403 error, i.e.:

fromJSON(rawToChar(translated$content))

gives:

$error
$error$code
[1] 403

$error$message
[1] "The request is missing a valid API key."

$error$errors
                                  message domain    reason
1 The request is missing a valid API key. global forbidden

$error$status
[1] "PERMISSION_DENIED"

Note: the "MYKEY" used above I have of course replaced with my created true API key.

Any ideas what's going on?

---

Update: the following does work for v2 of the API (but not v3). I was missing te unboxing in the JSON body and I seem to have to put the APIkey into the URL:

textbody <- toJSON(list(q = my_text,
                        target = "en"),
                   auto_unbox = TRUE)

translated <- POST(url = paste0("https://translation.googleapis.com/language/translate/v2?key=", my_key),
                   content_type("application/json"),
                   body = textbody,
                   encode = "json")