TrueLayer.Client SSRF when fetching payment or payment provider

TrueLayer.NET is the .Net client for TrueLayer. The vulnerability could potentially allow a malicious actor to gain control over the destination URL of the HttpClient used in the API classes. For applications using the SDK, requests to unexpected resources on local networks or to the internet could be made which could lead to information disclosure. The issue can be mitigated by having strict egress rules limiting the destinations to which requests can be made, and applying strict validation to any user input passed to the `truelayer-dotnet` library. Versions of TrueLayer.Client `v1.6.0` and later are not affected.