feat: Add support for Symantec ICAP

[enjeck]

This provides Symantec antivirus support

[icewind1991]

From what I can tell the main difference between this and the existing icap implementation is the handling of the X-Error-Code reply header. I'll look into adding that logic to the existing icap scanner instead of duplicating the logic.

[Philldomd]

Hi that is correct, all we did was to add error handling from Symantec as it sends 500 codes back. I also added a choice for password protected files as it does mark them in Symantec, not a virus but still 500 return code.

I was uncertain about these rows: https://github.com/nextcloud/files_antivirus/pull/375/commits/a99e80c715c8eb8af3ac4d00a44add867242342e#diff-a33d182d4905d83769450f1fc22983b023638ee35cec5d842f24ae390204a5f4R148-R149

It might be better to dont allow this files than mark them as unchecked.

[icewind1991]

I guess the best way forward is to introduce an "unable to scan" result (separate from the "try to rescan later") and let the admin configure to either allow or block those files. That would then also include password protected files.

[icewind1991]

wip: https://github.com/nextcloud/files_antivirus/pull/378

[AndyScherzinger]

@icewind1991 with #378 merged and afaik tested by the customer-feature-requests, can this PR be closed as bring obsolete? Cc @Philldomd for feedback.

[icewind1991]

Yes this can be closed, I'll try to do a release soon.

Edit: done