Validate login request and refactor login handling

RecNet.Domain/Configuration/IServerConfigRepository.cs

@@ -0,0 +1,10 @@
+using RecNet.Domain.Entities.Configuration;
+
+namespace RecNet.Domain.Repositories;
+
+public interface IServerConfigRepository
+{
+    Task<ServerConfig?> GetAsync(string key, CancellationToken ct = default);
+    Task SetAsync(string key, string value, CancellationToken ct = default);
+    Task SaveChangesAsync(CancellationToken ct = default);
+}