Added database handling of DeepL setting

I18N Commander/DataModel/Database/SettingDeepL.cs

@@ -0,0 +1,9 @@
+namespace DataModel.Database;
+
+public enum SettingDeepL
+{
+    DISABLED,
+    
+    USE_FREE_ACCOUNT,
+    USE_PRO_ACCOUNT,
+}

I18N Commander/DataModel/Database/SettingNames.cs

@@ -0,0 +1,6 @@
+namespace DataModel.Database;
+
+public static class SettingNames
+{
+    public static readonly string DEEPL_MODE = "DeepL Mode";
+}

I18N Commander/Processor/AppSettings.cs

@@ -0,0 +1,60 @@
+using DataModel.Database;
+using DataModel.Database.Common;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Processor;
+
+public static class AppSettings
+{
+    public static async Task SetDeepLMode(SettingDeepL mode)
+    {
+        // Convert the enum to its int value:
+        var intValue = (int)mode;
+        
+        // Get the database:
+        await using var db = ProcessorMeta.ServiceProvider.GetRequiredService<DataContext>();
+        
+        // Check, if the setting is already set:
+        if (await db.Settings.FirstOrDefaultAsync(n => n.Code == SettingNames.DEEPL_MODE) is {} existingSetting)
+        {
+            existingSetting.IntegerValue = intValue;
+            await db.SaveChangesAsync();
+        }
+        
+        // Does not exist, so create it:
+        else
+        {
+            var setting = new Setting
+            {
+                Code = SettingNames.DEEPL_MODE,
+                IntegerValue = intValue,
+            };
+            
+            await db.Settings.AddAsync(setting);
+            await db.SaveChangesAsync();
+        }
+    }
+
+    public static async Task<SettingDeepL> GetDeepLMode()
+    {
+        // Get the database:
+        await using var db = ProcessorMeta.ServiceProvider.GetRequiredService<DataContext>();
+        
+        // Check, if the setting is already set:
+        if (await db.Settings.FirstOrDefaultAsync(n => n.Code == SettingNames.DEEPL_MODE) is { } existingSetting)
+            return (SettingDeepL) existingSetting.IntegerValue;
+
+        // Does not exist, so create it:
+        var setting = new Setting
+        {
+            Code = SettingNames.DEEPL_MODE,
+            IntegerValue = (int)SettingDeepL.DISABLED,
+        };
+            
+        await db.Settings.AddAsync(setting);
+        await db.SaveChangesAsync();
+        
+        return (SettingDeepL) setting.IntegerValue;
+    }
+}