[FA-10] Adds user service and authentication service

FictionArchive.Service.UserService/GraphQL/Query.cs

@@ -0,0 +1,12 @@
+using FictionArchive.Service.UserService.Models.Database;
+using FictionArchive.Service.UserService.Services;
+
+namespace FictionArchive.Service.UserService.GraphQL;
+
+public class Query
+{
+    public async Task<IQueryable<User>> GetUsers(UserManagementService userManagementService)
+    {
+        return userManagementService.GetUsers();
+    }
+}