Refactor to introduce Govor.Application and Govor.Contracts layers

Moved service implementations and interfaces from Govor.API and Govor.Core to new Govor.Application and Govor.Contracts projects. Updated namespaces and references throughout the solution. Added custom exception classes for authentication and invite services. Adjusted dependency injection and project references to use the new structure. This refactor improves separation of concerns and prepares the codebase for better maintainability and scalability.

Govor.Application/Interfaces/Authentication/IAuthService.cs

@@ -0,0 +1,9 @@
+using Govor.Core.Models;
+
+namespace Govor.Application.Interfaces.Authentication;
+
+public interface IAccountService
+{
+    public Task<string> RegistrationAsync(string name, string password, Invitation invitation);
+    public Task<string> LoginAsync(string name, string password);
+}

Govor.Application/Interfaces/Authentication/IInvitesService.cs

@@ -0,0 +1,9 @@
+using Govor.Core.Models;
+
+namespace Govor.API.Services.Authentication.Interfaces;
+
+public interface IInvitesService
+{
+    public Task<string> GetRole(User user);
+    public Invitation Validate(string inviteCode);
+}

Govor.Application/Interfaces/Authentication/IJwtService.cs

@@ -0,0 +1,8 @@
+using Govor.Core.Models;
+
+namespace Govor.API.Services.Authentication.Interfaces;
+
+public interface IJwtService
+{
+    string GenerateJwtToken(User user);
+}