Fix: Risolto double-mapping negli External ID Relationships per Salesforce

- Implementata funzionalità completa External ID Relationships nell'interfaccia di mapping
- Corretto bug double-mapping: i campi sorgente usati per External ID non vengono più inclusi nei mapping normali
- Risolto errore MALFORMED_ID causato dall'invio duplicato di campi come proprietà dirette e nested objects
- Implementata logica corretta per relationship names: oggetti standard usano il nome diretto, custom objects usano suffisso __r
- Aggiunta UI a 3 colonne (Object, External ID Field, Source Field) per configurazione External ID Relationships
- Migrazione database per supporto External ID Relationships nei profili
- Aggiornato ProfileSaver.razor.cs per salvare/caricare External ID Relationships
- Aggiornato ScheduledProfileExecutionService.cs per gestire External ID nelle esecuzioni schedulate
- Formato JSON output corretto: { 'Account': { 'CardCode__c': 'V50000' } }

Documentazione: EXTERNAL_ID_RELATIONSHIPS_IMPLEMENTATION.md

CredentialManager/Services/DataCouplerProfileService.cs

@@ -109,6 +109,7 @@ public class DataCouplerProfileService : IDataCouplerProfileService
         existingProfile.DestinationTable = profile.DestinationTable;
         existingProfile.DestinationEndpoint = profile.DestinationEndpoint;
         existingProfile.FieldMappingJson = profile.FieldMappingJson;
+        existingProfile.ExternalIdRelationshipsJson = profile.ExternalIdRelationshipsJson;
         existingProfile.SourceKeyField = profile.SourceKeyField;
         existingProfile.UseRecordAssociations = profile.UseRecordAssociations;
         existingProfile.IsActive = profile.IsActive;
@@ -200,6 +201,41 @@ public class DataCouplerProfileService : IDataCouplerProfileService
             return new List<FieldMappingDto>();
         }
     }
+    
+    /// <summary>
+    /// Serializza la lista di External ID Relationships in JSON
+    /// </summary>
+    public string SerializeExternalIdRelationships(List<ExternalIdRelationshipDto>? relationships)
+    {
+        if (relationships == null || !relationships.Any())
+            return string.Empty;
+
+        return JsonSerializer.Serialize(relationships, new JsonSerializerOptions 
+        { 
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase 
+        });
+    }
+
+    /// <summary>
+    /// Deserializza il JSON delle External ID Relationships
+    /// </summary>
+    public List<ExternalIdRelationshipDto> DeserializeExternalIdRelationships(string? json)
+    {
+        if (string.IsNullOrWhiteSpace(json))
+            return new List<ExternalIdRelationshipDto>();
+
+        try
+        {
+            return JsonSerializer.Deserialize<List<ExternalIdRelationshipDto>>(json, new JsonSerializerOptions 
+            { 
+                PropertyNamingPolicy = JsonNamingPolicy.CamelCase 
+            }) ?? new List<ExternalIdRelationshipDto>();
+        }
+        catch
+        {
+            return new List<ExternalIdRelationshipDto>();
+        }
+    }
 
     /// <summary>
     /// Converte un DataCouplerProfile in DTO
@@ -226,6 +262,7 @@ public class DataCouplerProfileService : IDataCouplerProfileService
             DestinationTable = profile.DestinationTable,
             DestinationEndpoint = profile.DestinationEndpoint,
             FieldMappings = DeserializeFieldMappings(profile.FieldMappingJson),
+            ExternalIdRelationships = DeserializeExternalIdRelationships(profile.ExternalIdRelationshipsJson),
             SourceKeyField = profile.SourceKeyField,
             UseRecordAssociations = profile.UseRecordAssociations
         };
@@ -254,6 +291,7 @@ public class DataCouplerProfileService : IDataCouplerProfileService
             DestinationTable = dto.DestinationTable,
             DestinationEndpoint = dto.DestinationEndpoint,
             FieldMappingJson = SerializeFieldMappings(dto.FieldMappings),
+            ExternalIdRelationshipsJson = SerializeExternalIdRelationships(dto.ExternalIdRelationships),
             SourceKeyField = dto.SourceKeyField,
             UseRecordAssociations = dto.UseRecordAssociations,
             CreatedBy = createdBy