Changes since 0.5.0

SystemdBus

Call timeouts are converted correctly. A Duration timeout was multiplied by 10,000,000 instead of 1,000,000, so .seconds(1) waited 10 s. A zero or negative timeout is now 1 µs, since 0 means sd-bus's default, and one too large means no timeout.
Call timeouts fire. A call to a peer that never replied waited forever, whatever its timeout. The bus now keeps a timer armed for sd-bus's next deadline.
Struct values can be read from replies. A reply containing a struct (a(isb), a(iiay), …) failed with EBADMSG. Structs now decode as [any Sendable] of their fields, and byte arrays as [UInt8].
Calls can skip bus activation. callMethod, getProperty and getProperties take autoStart: Bool = true. With false, a call to a service that isn't running fails instead of starting it. getProperty and getProperties also take timeout:.
Private connections. SystemdBus.openSystem() and openUser() open a connection of their own rather than sharing the thread's default one. .system and .user are unchanged.

The package now has tests (SystemdTests). All changes are source-compatible. #14.