Rearrange the where clause for generated Client::new() constructors

[Michael-F-Bryan]

This PR rearranges the where clause on Client::new() to make it work with type inference and impl Trait better.

---

Clients currently explicitly require that an auth can be turned into a Box<dyn GetAccessToken>, but this doesn't play well with impl Trait and the impl GetAccessToken returned by google_api_auth::yup_oauth2::from_authenticator().

For example, I am trying to use the following code:

let app_secret: ApplicationSecret = args.load_app_secret()?;

let authenticator = DeviceFlowAuthenticator::builder(app_secret)
    .persist_tokens_to_disk(
        PROJECT_DIRS.cache_dir().join("token-cache.json"),
    )
    .build()
    .await
    .context("Unable to create the OAuth2 authenticator")?;


let scopes = vec!["https://www.googleapis.com/auth/cloud-translation"];
let get_access_token =
    google_api_auth::yup_oauth2::from_authenticator(authenticator, scopes);
let client = Client::new(get_access_token);

(original code)

And rustc fails with the unhelpful error message "the trait bound impl google_api_auth::GetAccessToken: std::convert::From<impl google_api_auth::GetAccessToken> is not satisfied"... Which doesn't make sense considering T: From<T>.

error[E0277]: the trait bound `impl google_api_auth::GetAccessToken: std::convert::From<impl google_api_auth::GetAccessToken>` is not satisfied
    --> cli\src\main.rs:27:30
     |
27   |     let client = Client::new(get_access_token);
     |                              ^^^^^^^^^^^^^^^^
     |                              |
     |                              expected an implementor of trait `std::convert::From<impl google_api_auth::GetAccessToken>`
     |                              help: consider borrowing here: `&get_access_token`
     |
    ::: C:\Users\mbryan\.cargo\git\checkouts\generated-f06055b20a4066fd\1f027cd\gen\translate\v3\lib\src\lib.rs:1237:12
     |
1237 |         A: Into<Box<dyn ::google_api_auth::GetAccessToken>>,
     |            ------------------------------------------------ required by this bound in `google_translate3::Client::new`
     |
     = note: required because of the requirements on the impl of `std::convert::From<impl google_api_auth::GetAccessToken>` for `std::boxed::Box<(dyn google_api_auth::GetAccessToken + 'static)>`
     = note: required because of the requirements on the impl of `std::convert::Into<std::boxed::Box<(dyn google_api_auth::GetAccessToken + 'static)>>` for `impl google_api_auth::GetAccessToken`

error: aborting due to previous error

This is linked to #24 in that the user experience for authentication isn't great.

[Michael-F-Bryan]

Thanks @ggriffiniii. Are you able to regenerate the files in google-apis-rs/generated with the new changes?

[mwilliammyers]

@Michael-F-Bryan, I will regenerate them.

[mwilliammyers]

PS this will change (I think in a breaking way) when we merge in the async branch because yup-oauth has breaking changes in 4.0...

[mwilliammyers]

@Michael-F-Bryan

I regenerated everything: google-apis-rs/generated@d53ef68