Add support for files endpoint

[xiaohua-scale]

1. Add support for files endpoint: https://docs.scale.com/reference#file-overview
2. Add an instruction_batch param for batch creation: https://docs.scale.com/reference#batch-overview
3. Add test for import_file & upload_file

unittest && e2e tested with the following code

import scaleapi
from scaleapi.tasks import TaskType

client = scaleapi.ScaleClient("<api_key>")


batch = "test-client-project-1-instruction-batch-1"
project = "test-client-project-1"


# Upload File
with open("test_image.png", "rb") as f:
    data = ("x", f)

    # Upload File
    payload = dict(project_name=project)
    upload_result = client.upload_file(
        file=data,
        project_name=project,
    )
    print(upload_result.__repr__())

# Import File
import_result = client.import_file(
    "https://static.scale.com/uploads/selfserve-sample-image.png",
    project_name=project,
)

print(import_result.__repr__())


client.create_batch(
    project=project,
    batch_name=batch,
    instruction_batch=True,
)

payload = dict(
    project=project,
    attachments=[
        {"type": "image", "content": import_result.attachment_url},
        {"type": "image", "content": upload_result.attachment_url},
    ],
    batch=batch,
)

client.create_task(task_type=TaskType.TextCollection, **payload)

client.finalize_batch(batch_name=batch)

[xiaohua-scale]

if you specify a files parameter (a dictionary), then requests will send a multipart/form-data POST instead of a application/x-www-form-urlencoded POST.

ref: https://stackoverflow.com/questions/12385179/how-to-send-a-multipart-form-data-with-requests-in-python

[fatihkurtoglu]

Looks good to me!