[FEATURE]: Add encoding to sql operator

[imhoffd]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

The sql operator's mapWith method lets us specify mappers for decoding from the database, but there are use cases where we need to encode. See the example below.

1. Add a decimalType custom type

import { Decimal } from 'decimal.js'
import { type CustomTypeParams, customType } from 'drizzle-orm/pg-core'

const decimalTypeParams: CustomTypeParams<{
  data: Decimal
  driverData: string | number
}> = {
  dataType() {
    return 'numeric(64, 32)'
  },

  toDriver(data) {
    return data.toString()
  },

  fromDriver(data): Decimal {
    return new Decimal(data)
  },
}

export const decimalType = customType(decimalTypeParams)

2. Query a column that uses it

// Example A: works great
eq(myTable.myDecimalCol, new Decimal("0"))

// Example B: driver error: invalid input syntax for type numeric: ""0""
eq(sql`abs(${myTable.myDecimalCol})`, new Decimal("0"))

// Example C: works, but not ideal imo
eq(sql`abs(${myTable.myDecimalCol})`, new Decimal("0").toString())

The issue in example B appears to be that it's not using the custom type's toDriver function, which is reasonable. However, there's no way to make it use it.

This would be useful in functions that apply a SQL operator to a column value, but don't change its resultant type, e.g. it would be very useful to be able to write a function like this where the column's mapFromDriverValue and mapToDriverValue are applied:

import {
  type AnyColumn,
  type GetColumnData,
  type SQL,
  type SQLWrapper,
  Column,
  is,
  sql,
} from 'drizzle-orm'

export const abs: {
  <T>(column: SQL.Aliased<T>): SQL<T>
  <TColumn extends AnyColumn>(
    column: TColumn,
  ): SQL<GetColumnData<TColumn, 'raw'>>
  <T extends SQLWrapper>(column: Exclude<T, SQL.Aliased | Column>): SQL
} = (column: SQL.Aliased): SQL => {
  return sql`abs(${column})`.mapWith(
    is(column, Column) ? column : (v: unknown) => v,
  )
}

LMK if I'm missing something! Thanks!