fix(fileRequest): use Guzzle's "sink" instead of stream

[oleksandr-nc]

I can reproduce locally such error(I was able to reproduce this even a year ago, but I was thinking that it is only on my local machine):
Allowed memory size of 536870912 bytes exhausted (tried to allocate 5000032 bytes) at /var/www/html/lib/private/Log/ExceptionSerializer.php#236

After that always syncing dies, as process crashes and flag onedrive_import_running does not get reset in the database for the next background jobs run.

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Why does memory error occur? (a guess)

The Nextcloud HTTP client is a thin wrapper around Guzzle 7.
With Guzzle, the stream => true flag does not stream the response to the passed resource; it only prevents the body from being-decoded, afaik.
The entire response is still buffered in memory before it is handed back as a Psr7\Stream.
When we then iterate over that stream with fread(), every 5 MB chunk we copy is duplicated – the buffered copy inside Guzzle plus your $chunk string – until PHP asks for another 5 MB and finally dies at ~512 MB.

The easiest way is to tell Guzzle to write directly to the file handler, with sink

I have tested this changes and now I do not see memory exhausted errors anymore.

[julien-nc]

💥 Nice discovery. We should avoid streaming from now on.