(www/R-gargle) Updated 1.4.0 to 1.5.0

# gargle 1.5.0

* gargle's existing unexported `secret_*()` functions are deprecated, in favor
  of new, exported `secret_*()` functions that are built on or inlined from
  httr2. The `vignette("managing-tokens-securely")` is updated to reflect the
  new, recommended strategy for encrypting secrets.
  - `secret_encrypt_json()` / `secret_decrypt_json()` are new gargle-specific
    functions.
  - `secret_write_rds()` / `secret_read_rds()`, `secret_make_key()`, and
    `secret_had_key()` are basically copies of their httr2 counterparts.
  - Legacy functions to move away from: `secret_pw_name()`, `secret_pw_gen()`,
    `secret_pw_exists()`, `secret_pw_get()`, `secret_can_decypt()`,
    `secret_read()`, `secret_write()`.
  - The new approach makes it much easier to use gargle functions to encrypt and
    decrypt credentials in a project that is *not* necessarily an R package.

* The transition from OAuth "app" to OAuth "client" is fully enacted now. This
  process tarted in v1.3.0, when the `"gargle_oauth_client"` class was
  introduced, to support the new pseudo-OOB auth flow. The deprecations are
  implemented to preserve backwards compatibility for some time. In this
  release, function, argument, and field names are all updated to the "client"
  terminology:

  - `init_AuthState(client =)` instead of `init_AuthState(app =)`
  - `AuthState$client` instead of `AuthState$app`
  - `AuthState$set_client()` instead of `AuthState$set_app()`
  - `gargle2.0_token(client =)` instead of `gargle2.0_token(app =)`
  - `credentials_user_oauth2(client =)` instead of
    `credentials_user_oauth2(app =)`

  A new `vignette("oauth-client-not-app")` explains how a wrapper package should
  adapt.

* When the `"gargle_verbosity"` option is set to `"debug"`, there are
  more debugging messages around user credentials. Specifically, more
  information is available on the email, OAuth client, and scopes,
  with the goal of better understanding why a cached token is (or is
  not) being used.

* `check_is_service_account()` is a new function for use in wrapper
  packages to throw a more informative error when a user provides JSON
  for an OAuth client to an argument that is expecting JSON for a
  service account.

* `response_process()` has improved handling of responses that
  represent an HTTP error with HTML content (as opposed to the
  expected and preferred JSON) (#254).

* `response_process(call = caller_env())` is a new argument that is
  passed along to various helpers, which can improve error reporting
  for user-facing functions that call `response_process()` (#255).


(mef)