Added DeepL API key setting

I18N Commander/Processor/AppSettings.cs

@@ -7,6 +7,8 @@ namespace Processor;
 
 public static class AppSettings
 {
+    #region DeepL Mode
+
     public static async Task SetDeepLMode(SettingDeepL mode)
     {
         // Convert the enum to its int value:
@@ -57,4 +59,58 @@ public static class AppSettings
         
         return (SettingDeepL) setting.IntegerValue;
     }
+
+    #endregion
+    
+    #region DeepL API Key
+    
+    public static async Task SetDeepLAPIKey(string apiKey)
+    {
+        // 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_API_KEY) is {} existingSetting)
+        {
+            existingSetting.TextValue = apiKey;
+            await db.SaveChangesAsync();
+        }
+        
+        // Does not exist, so create it:
+        else
+        {
+            var setting = new Setting
+            {
+                Code = SettingNames.DEEPL_API_KEY,
+                TextValue = apiKey,
+            };
+            
+            await db.Settings.AddAsync(setting);
+            await db.SaveChangesAsync();
+        }
+    }
+    
+    public static async Task<string> GetDeepLAPIKey()
+    {
+        // 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_API_KEY) is { } existingSetting)
+            return existingSetting.TextValue;
+        
+        // Does not exist, so create it:
+        var setting = new Setting
+        {
+            Code = SettingNames.DEEPL_API_KEY,
+            TextValue = string.Empty,
+        };
+            
+        await db.Settings.AddAsync(setting);
+        await db.SaveChangesAsync();
+        
+        return setting.TextValue;
+    }
+    
+    #endregion
 }