add support of remote storage

[badziyoussef]

Actually, the package is not compatible with django-storages, which is a valuable feature, as django can run in production in a scallable environment, actually with django-storages it raise (see screenshot bellow)

[badziyoussef]

@pfouque can we move forward with this PR? the bug is a real blocker when using Google Oauth2

[pfouque]

Hi @badziyoussef,
Firstly, It would be easier to merge two separate PR, with distinct purposes.

Additionally, merging doesn't necessarily mean a new release will be published soon.
So I'd recommend you, especially if it's urgent, to run your project using your own fork in the meantime (Multiple solutions exist to do so, with or without publishing to pypi).

[badziyoussef]

Hi @pfouque, I splitted to two separate PR as requested, if you can check

[pfouque]

Hi @badziyoussef,
Thanks for splitting the PR but this implementation is what we had previously and it was generating some trouble.
According to PR #273 there was an issue when too many files were opened.
I assume it was solved by using "with" which garantee to have only one file opened at once.
To solve both issues at once, we need to find a way to close files after processing them, using a remote-storage compatible accessor...

[pfouque]

Needs to be tested, but it's probably enough to make it compatible with remote storage

Suggested change

	output = BytesIO()
	encode_quopri(
	BytesIO(
	attachment.document.read()
	),
	output,
	quotetabs=True,
	header=False,
	)
	new.set_payload(
	output.getvalue().decode().replace(' ', '=20')
	)
	with attachment.document.open('rb') as f:
	output = BytesIO()
	encode_quopri(
	BytesIO(
	f.read()
	),
	output,
	quotetabs=True,
	header=False,
	)
	new.set_payload(
	output.getvalue().decode().replace(' ', '=20')

[pfouque]

Needs to be tested, but it's probably enough to make it compatible with remote storage

Suggested change

	new.set_payload(attachment.document.read())
	with attachment.document.open('rb') as f:
	new.set_payload(f.read())