All tests and invocations of `add_stage` actually pass a valid
options dictionary. Thefore move the `options` args before
the `sources` arg and remove the default value (`None`).
Instead of having build pipelines nested within the pipeline it is
the build pipeline for, the nested structure is transferred into a
flat list of pipelines. As a result the recursion is gone and all
the pipelines and trees are build one after the other. This is now
possible since floating objects are kept alive by the store itself
and all trees that are being built are transparently via them.
The immediate result dictionary changed accordingly. To keep the
JSON output of osbuild the same, the result is now routed through
a format specific converter.
Additionally, the v1 format module gained a function to retrieve
the global tree_id and output_id. With the new models those global
ids will go away eventually and thus need to go through the format
specific code.
Instead of a pipeline, describe now takes a Manifest instance.
The reason is that a manifest fully describes the build, which
includes the sources. Now that the describe function takes the
manifest, the sources can be included as well.
Adapt the tests to refelect that change.
The 'Manifest' class represents what to build and the necessary
sources to do so. For now thus it is just a combination of the
pipeline the source options.
The description of a pipeline is format dependent and thus needs
to be located at the specific format module.
Temporarily remove two tests; they should be added back to a format
specific test suit.
Instead of having the pipeline and the source option as separate
arguments, the load function now takes the full manifest, which
has those two items combined.
The validation of the manifest descritpion is eo ipso format
specific and thus belongs into the format specific module.
Adapt all usages throughout the codebase to directly use the
version 1 specific function.
Extract the code that loads a pipeline from a pipeline description,
i.e. a manifest, into a new module inside a new 'formats' package.
The idea is to have different descriptions, i.e. different formats,
for the same internal representation. This allows changing the
internal representation, i.e. data structures, but still having the
same external description.
Later a new description might be added that better matches the new
internal representation.
