Fixed self-hosted providers not using their stored API key (#959)

Co-authored-by: Dominic Neuburg <dominic@done-work.com>
Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/Validation/ProviderValidation.cs

@@ -49,16 +49,20 @@ public sealed class ProviderValidation
 
     public string? ValidatingAPIKey(string apiKey)
     {
-        if(this.GetProvider() is LLMProviders.SELF_HOSTED)
-            return null;
-        
+        // A key which could not be stored in or removed from the operating system has to reach the
+        // user for every provider. Self-hosted providers are exempt from having to name a key at
+        // all, not from being told that the one they named was lost on the way:
         var apiKeyStorageIssue = this.GetAPIKeyStorageIssue();
         if(!string.IsNullOrWhiteSpace(apiKeyStorageIssue))
             return apiKeyStorageIssue;
 
+        // A self-hosted server may well run without any key, so an empty field is fine for it:
+        if(this.GetProvider() is LLMProviders.SELF_HOSTED)
+            return null;
+
         if(string.IsNullOrWhiteSpace(apiKey))
             return TB("Please enter an API key.");
-        
+
         return null;
     }