Filter by the concatenation of two columns

Nadie ha tomado este issue todavía.

## Suggestion

It would be nice to be able to filter a Model by the concatenation of two columns.
I mean, to be able to replicate this type of SQL query:
```sql
SELECT * FROM User WHERE CONCAT(name, ' ', lastName) LIKE '%PARTIAL FULLNAME%'
```

## Use Cases

The most common example is filtering a User model by its full name when it's stored in two columns (name, lastName).
Currently, the only way this is possible (AFAIK) is by sending the RAW query, which makes it almost incompatible with adding more filters.

## Examples
Table example:
| id | name | lastName |
|----|---------|----------|
| 1 | Jackson | Bell |
| 2 | Sarah | Parker |
| 3 | Mason | Brown |

Example of one (possible) implementation of filter object:
```json
{
"limit": 10,
"offset": 0,
"where": {
"leavingDate": null,
"concat": {
"eq": "%on B%",
"separator": " ",
"columns": [
"name",
"lastName"
]
}
}
}
```

Should return:
| id | name | lastName |
|----|---------|----------|
| 1 | Jackson | Bell |
| 3 | Mason | Brown |

## Acceptance criteria

TBD - will be filled by the team.

Comienza revisando el objeto de filtro `where.concat` propuesto y cómo los filtros de repositorio gestionan actualmente las consultas sin procesar. Aclara con el equipo los criterios de aceptación, incluidas las columnas compatibles, los separadores, los operadores de comparación y el comportamiento de la base de datos. La tarea estará terminada cuando el filtrado por concatenación funcione junto con otros filtros y exista una verificación documentada.

Escrito por el modelo de indexación a partir del texto del issue.