Provide full set of systemd's Manager API

[engelmi]

BlueChi currently only provides a subset of the APIs provided by systemd's Manager API (https://www.freedesktop.org/wiki/Software/systemd/dbus/) - method, signal and properties. The following table contains a comparison between both - evaluating if the API in systemd exists in BlueChi, if it should be added and a link to the GitHub issue where it is tackled.

Note:

• If the API should be implemented is up for discussion.
• Please refer to the documentation page for systemd for details about the individual method, signal or property.

Feature table

Type	Name	Exists?	Should Implement?	GH issue
method	GetUnit	no	no
method	GetUnitByPID	no	no
method	LoadUnit	no	maybe
method	StartUnit	yes
method	StartUnitReplace	no	maybe
method	StopUnit	yes
method	ReloadUnit	yes
method	RestartUnit	yes
method	TryRestartUnit	no	no
method	ReloadOrRestartUnit	no	no
method	ReloadOrTryRestartUnit	no	no
method	KillUnit	no	yes	#938
method	ResetFailedUnit	no	yes	#932
method	GetJob	no	no
method	CancelJob	yes
method	ClearJobs	no	yes
method	ResetFailed	no	yes	#932
method	ListUnits	yes
method	ListJobs	no	yes
method	Subscribe	yes
method	Unsubscribe	no	no
method	CreateSnapshot	no	maybe
method	RemoveSnapshot	no	maybe
method	Reload	yes
method	Reexecute	no	no
method	Exit	no	no
method	Reboot	no	no
method	PowerOff	no	no
method	Halt	no	no
method	KExec	no	no
method	SwitchRoot	no	no
method	SetEnvironment	no	maybe
method	UnsetEnvironment	no	maybe
method	UnsetAndSetEnvironment	no	maybe
method	ListUnitFiles	yes
method	GetUnitFileState	no	yes	#934
method	EnableUnitFiles	yes
method	DisableUnitFiles	yes
method	ReenableUnitFiles	no	maybe
method	LinkUnitFiles	no	maybe
method	PresetUnitFiles	no	maybe
method	MaskUnitFiles	no	maybe
method	UnmaskUnitFiles	no	maybe
method	SetDefaultTarget	no	yes	#944
method	GetDefaultTarget	no	yes	#944
method	SetUnitProperties	yes
method	StartTransientUnit	no	yes
signal	UnitNew	yes
signal	UnitRemoved	yes
signal	JobNew	yes
signal	JobRemoved	yes
signal	StartupFinished	no	no
signal	UnitFilesChanged	no	yes
signal	Reloading	no	yes