Add an as_azure_token() for compatibility with AzureR packages.

This commit introduces a standalone `as_azure_token()` that converts
the httr2 format to one that works out of the box with AzureR packages.
For example:

    token <- NULL
    if (has_viewer_token()) {
      token <- as_azure_token(connect_viewer_token())
    }
    Microsoft365R::list_sharepoint_sites(token = token)

Fixes #4.

Signed-off-by: Aaron Jacobs <aaron.jacobs@posit.co>

Author: atheriel

DESCRIPTION

@@ -13,8 +13,10 @@ License: MIT + file LICENSE
 Imports:
     cli,
     httr2 (>= 1.1.0),
+    R6,
     rlang (>= 1.1.0)
 Suggests:
+    AzureAuth,
     testthat (>= 3.0.0),
     withr
 Encoding: UTF-8

NAMESPACE

@@ -1,5 +1,6 @@
 # Generated by roxygen2: do not edit by hand
 
+export(as_azure_token)
 export(connect_service_account_token)
 export(connect_viewer_token)
 export(has_service_account_token)
@@ -8,3 +9,4 @@ export(local_mocked_connect_responses)
 export(with_mocked_connect_responses)
 import(httr2)
 import(rlang)
+importFrom(R6,R6Class)

R/azure-token.R

@@ -0,0 +1,61 @@
+#' Convert a token to the AzureAuth format
+#'
+#' Wraps an [httr2::oauth_token] in an [AzureAuth::AzureToken] for use with the
+#' AzureR package ecosystem.
+#'
+#' @param token An [httr2::oauth_token].
+#' @param resource The Azure resource this token is associated with, or `NULL`
+#'   if this is unknown.
+#' @returns An R6 class that inherits from `AzureToken`.
+#' @examplesIf FALSE
+#' token <- NULL
+#' if (has_viewer_token()) {
+#'   token <- as_azure_token(connect_viewer_token())
+#' }
+#'
+#' # For example, when using the Microsoft365R package:
+#' # Microsoft365R::list_sharepoint_sites(token = token)
+#' @export
+as_azure_token <- function(token, resource = NULL) {
+  rlang::check_installed("AzureAuth", reason = "for AzureR compatibility")
+  ConnectAzureToken$new(token, resource = resource)
+}
+
+# An AzureR-interoperable token class.
+ConnectAzureToken <- R6Class(
+  "ConnectAzureToken",
+  inherit = AzureAuth::AzureToken,
+  public = list(
+    initialize = function(token, resource = NULL) {
+      self$credentials <- unclass(token)
+      self$auth_type <- "external"
+      super$initialize(
+        resource = resource,
+        app = "Posit Connect",
+        # Inaccurate but necessary to avoid errors.
+        tenant = "common",
+        version = 2,
+        aad_host = NA,
+        token_args = list(),
+        # This triggers the "dummy" workflow that skips calling out to Azure.
+        use_cache = NA
+      )
+    },
+
+    # Tokens must be refreshed via connectcreds library calls instead.
+    can_refresh = function() FALSE,
+
+    # Custom validation.
+    validate = function() {
+      if (is.null(self$credentials$expires_at)) {
+        TRUE
+      } else {
+        (as.integer(Sys.time()) + 5) > self$credentials$expires_at
+      }
+    }
+  ),
+  private = list(
+    # Necessary to avoid "Do not call this constructor directly" errors.
+    initfunc = function(...) {}
+  )
+)

R/connectcreds-package.R

@@ -4,5 +4,6 @@
 ## usethis namespace: start
 #' @import httr2
 #' @import rlang
+#' @importFrom R6 R6Class
 ## usethis namespace: end
 NULL