Description of the issue

Docker Compose v2 (compose-go) is stripping out escape characters when inside of a quoted string in a command (might happen in other circumstances).

If it's not in a quoted string, they are left as-is. For example, command: printf 'Hello\tworld\n' works while command: sh -c "printf 'Hello\tworld\n'" does not.

Context information (for bug reports)

• Using Compose V2 docker compose ...
• Using Compose V1 docker-compose ...

Output of docker(-)compose version

Docker Compose version v2.0.0-rc.2

Output of docker version

Client:
 Cloud integration: 1.0.17
 Version:           20.10.8
 API version:       1.41
 Go version:        go1.16.6
 Git commit:        3967b7d
 Built:             Fri Jul 30 19:55:20 2021
 OS/Arch:           darwin/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.8
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.6
  Git commit:       75249d8
  Built:            Fri Jul 30 19:52:10 2021
  OS/Arch:          linux/amd64
  Experimental:     true
 containerd:
  Version:          1.4.9
  GitCommit:        e25210fe30a0a703442421b0f60afac609f950a3
 runc:
  Version:          1.0.1
  GitCommit:        v1.0.1-0-g4144b63
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Output of docker-compose config
w/ v2 (v2.0.0-rc.2):

services:
  hello-world:
    command:
    - sh
    - -c
    - printf 'Hellotworldn'
    image: busybox
    networks:
      default: null
networks:
  default:
    name: escape-repro_default

w/ v1 (1.29.2, build 5becea4):

services:
  hello-world:
    command: sh -c "printf 'Hello\tworld\n'"
    image: busybox
version: '3.9'

Steps to reproduce the issue

1. Use an escape sequence (e.g. \t or \n) inside of a quoted string in command

Observed result

• Docker Compose v2 (compose-go) strips out the \ characters

Expected result

• Docker Compose leaves the \ characters as-is

Stacktrace / full error message

n/a

Additional information

n/a