Implement field alias Field#as

[mtkachenk0]

For API that have logic changes inside but the structures cannot be modified (backward compatibility) would be usefull to implement method as for field

schema do 
  field(:from_id).present.as(:from_identifier)
end 

the result should not contain from_id but contain from_identifier with the very value of from_id

# Input:
{from_id: 1}
# Output:
{from_identifier: 1}