Refactor DTO classes to use model_config with ConfigDict for attribute handling

- Updated multiple DTO classes across various modules to replace the `Config` class with `model_config = ConfigDict(from_attributes=True)`.
- This change enhances consistency in attribute handling and aligns with the latest Pydantic practices.
- Adjusted error handling in core modules to change status codes from `HTTP_422_UNPROCESSABLE_ENTITY` to `HTTP_422_UNPROCESSABLE_CONTENT` for improved clarity in validation responses.

backend/api/v1/modules/a24/fa/fa_item_lines/dto.py

@@ -60,8 +60,7 @@ class FaLineItemCreateDTO(BaseModel):
     own_equipment: Optional[bool] = Field(None, description="Equipo propio")
     omit_annex31: Optional[bool] = Field(None, description="Omitir en Anexo 31")
 
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)
 
 
 class FaLineItemUpdateDTO(BaseModel):
@@ -112,8 +111,7 @@ class FaLineItemUpdateDTO(BaseModel):
     own_equipment: Optional[bool] = Field(None, description="Equipo propio")
     omit_annex31: Optional[bool] = Field(None, description="Omitir en Anexo 31")
 
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)
 
 
 class FaLineItemResponseDTO(BaseModel):
@@ -164,5 +162,4 @@ class FaLineItemResponseDTO(BaseModel):
     created_at: datetime = Field(..., description="Fecha de creación")
     updated_at: datetime = Field(..., description="Fecha de actualización")
 
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)