Improve performance of coopering file data

[kozmod]

The current realization of the File (config package) use string type for keeping raw file data:

type File struct {
	Path  string  `yaml:"path"`
	Data  *string `yaml:"data"` 👈🏻👈🏻👈🏻
	Get   *Get    `yaml:"get"`
	Local *string `yaml:"local"
}

Data casts to []byte to creating domain entity (entity.DataFile):

...
		var producer entity.FileProducer
		switch {
		case f.Data != nil:
			file := entity.DataFile{
				FileInfo: tmpl,
				Data:     []byte(*f.Data),, 
			}
...

These conversions create a new slice or string, and therefore have time complexity proportional to the number of bytes that are processed.

import (
	"github.com/kozmod/progen/internal/entity"
	"testing"
)

const x = `matrix:
 version: 1.19
steps:
 name: Setup Go 1.19`

var fd = func(d FileData) *FileData { return &d }(FileData(`matrix:
 version: 1.19
steps:
 name: Setup Go 1.19`))

func Benchmark_copy_string(b *testing.B) {
	b.ReportAllocs()
	res := entity.DataFile{}
	for i := 0; i < b.N; i++ {
		res = entity.DataFile{Data: *fd}
	}
	_ = res
}

func Benchmark_copy_pointer_of_bytes(b *testing.B) {
	b.ReportAllocs()
	res := entity.DataFile{}
	for i := 0; i < b.N; i++ {
		res = entity.DataFile{Data: []byte(x)}
	}
	_ = res
}

cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Benchmark_copy_string
Benchmark_copy_string-12              	1000000000	         0.5203 ns/op	       0 B/op	       0 allocs/op
Benchmark_copy_pointer_of_bytes
Benchmark_copy_pointer_of_bytes-12    	38351860	        27.81 ns/op	      64 B/op	       1 allocs/op

Changing string to []byte will be more efficient

type File struct {
	Path  string    `yaml:"path"`
	Data  *[]byte `yaml:"data"`
	Get   *Get      `yaml:"get"`
	Local *string   `yaml:"local"`
}