Since .NET dynamically loads libicu, it is not prone to ABI breakage and can load virtually any version.
However, there is no `Depends: libicu*` option in Debian packages, so we need the explicit package version. This is prone to breaking as new Debian version bump the version number.
This PR changes the `Depends:` to `Recommends:` so `libicu` is installed if possible, but does not prevent installation.
For cases where the is no `libicu` on the system, there is now a `preinst` script which will warn if the library is missing, but not prevent installation.
The warning should only show in Docker images or similar slim contexts, as `libicu` is otherwise installed with the base system.
This updates VSS to default use Vanara in favor of AlphaVSS which is no longer maintained.
The build for Vanara requires targeting `net8.0-windows7.0`, which will cause significant build overhead and complexity for cross platform builds.
To counter this, the setup is to have a single project, `Duplicati.Library.WindowsModules`, that is targeting `net8.0-windows7.0`.
The output from this project is then hoisted into the TrayIcon project for Windows builds so the files are available when debugging on Windows.
A top-level dummy executable project is added to ensure the project always builds.
The built modules are then loaded with reflection when requested.
With the use of Vanara there is now also support for using BackupRead to read files without making a VSS snapshot.
With BackupRead, it is possible to read locked files, but it still requires the SeBackupPrivilege as VSS does as well.
Unfortunately, the `vssapi.dll` file is not shipped for Arm64 on Windows, so even with Vanara this will not work, and only WMIC is supported on Arm64.
A workaround is to run Duplicati with x64 emulation if more advanced VSS features are needed (HyperV and MSSQL support).
This PR also updates options and filters out unsupported options for each operating system, so options that are not supported by the current OS are not reported and will give warnings if they are used, as opposed to just being ignored.
The release builder project has been updated to exclude the unused project, and purge unwanted outputs.
This adds a CI test for building releases so we know in advance if package versions are out-of-order.
This also sets the primary project for CLI to the Server as that covers more than the CLI project.
The logic is reverted to build each project into a build folder, and then copy the files into a shared common folder.
An additional check examines the log output and checks that there are no debug builds performed or used.
When building a release, it is now possible to also offer that release in "lower" channels, meaning the stable release will show as an update to instances running beta or experimental.
Kenneth Skovhede