OAuth2Helper not sending custom params on client credentials flow

[softwaresale]

Hello! I am currently using this package to interface with the Auth0 Management API. That flow uses the client credentials flow. Auth0 requires that you send an audience parameter when requesting a flow, but it appears that the following function:

oauth2_client/lib/oauth2_helper.dart

Lines 115 to 122 in 36f7e70

	} else if (grantType == clientCredentials) {
	tknResp = await client.getTokenWithClientCredentialsFlow(
	clientId: clientId,
	//The clientSecret param can't be null at this point... It has been validated by the above _validateAuthorizationParams call...
	clientSecret: clientSecret!,
	customHeaders: accessTokenHeaders,
	scopes: scopes);
	} else if (grantType == implicitGrant) {

does not send the custom parameters provided. Is this intentional? If not, it would be nice if client credentials flow can support custom auth token parameters. I can submit a PR for this feature if I should make the change. Thanks!