refactor: Common download operation

[adrien-coye]

We can push the refactor further and share the boilerplate of all DownloadOperations.

I did not rewrite old code that might need further rewrite. This is just code factorisation.

Intended to be reviewed per commit.

Root PR: #1311

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[PhilippeWeidmann]

LGTM.

One question, I'm a bit on the fence regarding the @unchecked Sendable for:

• DownloadOperation
• DownloadArchiveOperation

The other operations are fine because they don't have additional mutable state. However in the case of DownloadArchiveOperation we rely on the task that urlSession should be thread safe and calls in a queue downloadCompletion and assigns archiveUrl but nothing protects archiveUrl from being assigned elsewhere.

I won't request changes but this is something we have to keep in mind when using @unchecked

[adrien-coye]

Discussed regarding the @unchecked Sendable used with legacy Obj-c code.
Do not use it with legacy code without an audit, else do not use it and keep a warning, which make sense.