Make IsNative always true for echo; rethrow on invalid argument rpc e…

…xception when src and trg language are not the same for echo (#444)

src/Echo/src/EchoTranslationEngine/TranslationEngineServiceV1.cs

@@ -316,7 +316,7 @@ ServerCallContext context
     )
     {
         return Task.FromResult(
-            new GetLanguageInfoResponse { InternalCode = request.Language + "_echo", IsNative = false, }
+            new GetLanguageInfoResponse { InternalCode = request.Language + "_echo", IsNative = true, }
         );
     }
 

src/Serval/src/Serval.Translation/Services/EngineService.cs

@@ -149,6 +149,18 @@ public override async Task<Engine> CreateAsync(Engine engine, CancellationToken
                 IsModelPersisted = createResponse.IsModelPersisted
             };
         }
+        catch (RpcException rpcex)
+        {
+            await Entities.DeleteAsync(engine, CancellationToken.None);
+            if (rpcex.StatusCode == StatusCode.InvalidArgument)
+            {
+                throw new InvalidOperationException(
+                    $"Unable to create engine {engine.Id} because of an invalid argument: {rpcex.Status.Detail}",
+                    rpcex
+                );
+            }
+            throw;
+        }
         catch
         {
             await Entities.DeleteAsync(engine, CancellationToken.None);