Use Arrays insted of Lists for better performance

src/MistoxWebsite.Server/Services/DatabaseService/AccountInventory.cs

@@ -9,7 +9,7 @@ using System.Data.Common;
 namespace MistoxWebsite.Server.Services.DatabaseService {
     public partial class DatabaseService {
 
-        public async Task<List<UserInventory>> GetInventory( Account account, Product product ) {
+        public async Task<UserInventory[]> GetInventory( Account account, Product product ) {
             List<UserInventory> list = new List<UserInventory>();
             using( MySqlConnection connection = GetConnection() ) {
                 connection.Open();
@@ -40,7 +40,7 @@ namespace MistoxWebsite.Server.Services.DatabaseService {
                     }
                 }
             }
-            return list;
+            return list.ToArray();
         }
 
         async Task UpdateInventory( MySqlConnection connection, AccountInventory item ) {

src/MistoxWebsite.Server/Services/DatabaseService/Receipt.cs

@@ -6,7 +6,7 @@ using System.Data.Common;
 namespace MistoxWebsite.Server.Services.DatabaseService {
     public partial class DatabaseService {
 
-        public async Task<List<Receipt>> GetAllReceipts( Account account ) {
+        public async Task<Receipt[]> GetAllReceipts( Account account ) {
             List<Receipt> receipts = new List<Receipt> ();
             using( MySqlConnection connection = GetConnection() ) {
                 connection.Open();
@@ -43,10 +43,10 @@ namespace MistoxWebsite.Server.Services.DatabaseService {
                     }
                 }
             }
-            return receipts;
+            return receipts.ToArray();
         }
 
-        public async Task<List<( Receipt, Product )>> GetAllReceiptsJoinedToProduct( Account account ) {
+        public async Task<( Receipt, Product )[]> GetAllReceiptsJoinedToProduct( Account account ) {
             List<( Receipt, Product )> join = new();
             using( MySqlConnection connection = GetConnection() ) {
                 connection.Open();
@@ -100,7 +100,7 @@ namespace MistoxWebsite.Server.Services.DatabaseService {
                     }
                 }
             }
-            return join;
+            return join.ToArray();
         }
 
         public async Task<Receipt?> GetReceipt( Account account, Product game ) {