DRF batch requests

Quick start

examples:

curl -X POST \
  http://127.0.0.1:8000/batch/ \
  -H 'cache-control: no-cache' \
  -H 'content-type: application/json' \
  -d '{"batch": [
    {
        "method": "get",
        "relative_url": "/test/",
        "name": "yolo"
    },
    {
        "method": "post",
        "relative_url": "/test/?id={result=yolo:$.id}&ids={result=yolo:$.data.*.id}",
        "body": {"data": {"id": "{result=yolo:$.id}", "ids": "{result=yolo:$.data.*.id}"}, "test": "yolo"}
    },
    {
        "method": "post",
        "relative_url": "/test/",
        "body": "{\"data\": 42}",
        "omit_response_on_success": true
    },
    {
        "method": "options",
        "relative_url": "/test/"
    }
]
}'

using file uploading

curl -X POST \
  http://127.0.0.1:8000/batch/ \
  -H 'cache-control: no-cache' \
  -H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW' \
  -F 'batch=[
    {
        "method": "get",
        "relative_url": "/test/",
        "name": "yolo"
    },
    {
        "method": "post",
        "relative_url": "/test/?id={result=yolo:$.id}&ids={result=yolo:$.data.*.id}",
        "body": {"data": "{result=yolo:$.data.*.id}", "test": "yolo"},
        "attached_files":{"file": "a.jpg"}
    },
    {
        "method": "post",
        "relative_url": "/test/",
        "body": "{\"data\": 42}",
        "omit_response_on_success": true,
        "attached_files":["a.jpg", "b.png"]
    },
    {
        "method": "options",
        "relative_url": "/test/"
    }
]' \
  -F b.png=@2476.png \
  -F a.jpg=@check_133.pdf

Future features:

• add support for requests pipelining. use responses as arguments to next requests (done)
• build graph based on requests dependencies & run simultaneously independent.
• [STRIKEOUT:switchable atomic support. true - all fails if something wrong. else - fail only dependent (can be very hard to support on front-end side, but for now seems as good feature)] run all requests in single transaction. (done)
• [STRIKEOUT:use native django. we don't use complicated things that require drf for work. all can be done with "naked" django.] (since we validate requests with drf serializers, it's better to leave as it is).
• support files uploading (done)

Dependencies:

• Django starting from 2.2
• Django rest framework