Brightspace does not support multiple aud values

[alvan]

Related to this closed issue: #46

Now in 2024, we found in actual testing that Brightspace allows using the OAuth2 Access Token URL as the value of aud to obtain access tokens. At the same time, Brightspace does not support having two different values ​​in the aud array, which may cause its server-side 500 internal error.

So the current method cannot get access token from the Brightspace API.

lib-lti1p3-core/src/Service/Client/LtiServiceClient.php

Lines 216 to 219 in bef0d5f

	MessagePayloadInterface::CLAIM_AUD => [
	$registration->getPlatform()->getAudience(),
	$registration->getPlatform()->getOAuth2AccessTokenUrl(),
	]

On the contrary, just using the OAuth2 Access Token URL as aud works on most platforms including Canvas, saltire and Brightspace. This was the default implementation in earlier releases.

    // $registration->getPlatform()->getAudience(),
    $registration->getPlatform()->getOAuth2AccessTokenUrl(),