Provide server side of the portals interfaces

[bilelmoussaoui]

This would allow people to write a portals implementations in rust.

Very low priority, just in case might want to work on this

• org.freedesktop.impl.portal.Access — Interface for presenting an access dialog
• org.freedesktop.impl.portal.Account — Backend for the portal for obtaining user information
• org.freedesktop.impl.portal.AppChooser — Interface for choosing an application
• org.freedesktop.impl.portal.Background — Background portal backend interface
• org.freedesktop.impl.portal.Clipboard — Clipboard portal backend interface
• org.freedesktop.impl.portal.DynamicLauncher — Dynamic launcher portal backend interface
• org.freedesktop.impl.portal.Email — Email portal backend interface
• org.freedesktop.impl.portal.FileChooser — File chooser portal backend interface
• org.freedesktop.impl.portal.GlobalShortcuts
• org.freedesktop.impl.portal.Inhibit — Inhibit portal backend interface
• org.freedesktop.impl.portal.InputCapture — Input capture portal backend interface
• org.freedesktop.impl.portal.Lockdown — Lockdown backend interface
• org.freedesktop.impl.portal.Notification — Notification portal backend interface
• org.freedesktop.impl.portal.PermissionStore — Database to store permissions
• org.freedesktop.impl.portal.Print — Print portal backend interface
• org.freedesktop.impl.portal.RemoteDesktop — Remote desktop portal backend interface
• org.freedesktop.impl.portal.Request — Shared request interface
• org.freedesktop.impl.portal.ScreenCast — Screen cast portal backend interface
• org.freedesktop.impl.portal.Screenshot — Screenshot portal backend interface
• org.freedesktop.impl.portal.Secret — Secret portal backend interface
• org.freedesktop.impl.portal.Session — Shared session interface
• org.freedesktop.impl.portal.Settings — Settings portal backend interface
• org.freedesktop.impl.portal.Wallpaper — Portal for setting the desktop's Wallpaper