GHSA-grfp-q2mm-hfp6

### Impact

Before version v0.34.1, the OAuth 2.0 Client's registered redirect URLs and the redirect URL provided at the OAuth2 Authorization Endpoint where compared using `strings.ToLower` while they should have been compared with a simple string match:

1. Registering a client with allowed redirect URL `https://example.com/callback` 2. Performing OAuth2 flow and requesting redirect URL `https://example.com/CALLBACK` 3. Instead of an error (invalid redirect URL), the browser is redirected to `https://example.com/CALLBACK` with a potentially successful OAuth2 response, depending on the state of the overall OAuth2 flow (the user might still deny the request for example).