services/oauth2/access_token_validation_service#sufficent_scope?, scopes...

services/oauth2/access_token_validation_service#sufficent_scope?, scopes array should be string.

When comparing two sets, they mismatch and it shows below.

```ruby
    #<Set: {:red}>
    #<Set: {"red"}>
```

This fix will force scopes array to string.