Allows stages to access file systems provided by devices.
This makes mount handling transparent to the stages, i.e.
the individual stages do not need any code for different
file system types and the underlying devices.
A new host service that provides device functionality to stages.
Since stages run in a container and are restricted from creating
device nodes, all device handling is done in the main osbuild
process. Currently this is done with the help of APIs and RPC,
e.g. `LoopServer`. Device host services on the other hand allow
declaring devices in the manifest itself and then osbuild will
prepare all devices before running the stage. One desired effect
is that it makes device handling transparent to the stages, e.g.
they don't have to know about loopback devices, LVM or LUKS.
Another result is that specific device handling is now modular
like Inputs and Source are and thus moved out of osbuild itself.
Using the "$schema" without any specific version has been
deprecated[1] and will lead to warnings like:
DeprecationWarning: The metaschema specified by
$schema was not found. Using the latest draft to validate,
but this will raise an error in the future
Fix this by pointing $schema to "draft-07", which is the latest
version fully supported the jsonschema python package, that is
being used internally.
[1]
"The possibility to declare $schema without specific version
(http://json-schema.org/schema#) was deprecated after Draft 4
and should no longer be used."
https://json-schema.org/understanding-json-schema/reference/schema.html
This adds a non-binding, documentational-only json-schema to
schemas/osbuild1.json which describes the format of the pipeline
manifest taken as input to osbuild. This is currently for
documentational purposes, but is definitely open to be used for actual
runtime verification.
The manifest does not describe options to assemblers, stages, or
sources. These are left as arbitrary json-objects and need separate
validation, if required. Note that most stages already contain an
embedded schema for their parameters.
