pk-backend-spawn: Support 'pk_backend_job_details_full()'

[sidt4]

Please refer commit log.

All changes tested on latest Solus GNOME.

Fixes: #771

[sidt4]

Tested on top of 69cd3a1.

This MR will work with python backends which use the old or the new details_full API, hence backward compatible as shown below.

Without download_bytes argument:

/usr/share/PackageKit/helpers/eopkg/eopkgBackend.py:

    self.details(pkg_id, pkg.summary, ",".join(pkg.license), group, description, homepage, size)

sid@solus-gnome ~ $ pkcon get-details 0ad-data
Resolving                               [=========================]         
Getting details                         [=========================]         
Querying                                [=========================]         
Finished                                [=========================]         
Package description
  package:       0ad-data-0.27.0-11.x86_64
  summary:       Cross-platform, 3D and historically-based real-time strategy game (data files)
  license:       GPL-2.0-or-later,CCPL
  group:         games
  download size: unknown
  size:          3.5 GB (3,526,938,164 bytes)
  url:           https://play0ad.com
  description:   Cross-platform, 3D and historically-based real-time strategy game (data files)
sid@solus-gnome ~ $ 

With download_bytes argument:

/usr/share/PackageKit/helpers/eopkg/eopkgBackend.py:

    self.details(pkg_id, pkg.summary, ",".join(pkg.license), group, description, homepage, size, dl_size)

sid@solus-gnome ~ $ pkcon get-details 0ad-data
Resolving                               [=========================]         
Getting details                         [=========================]         
Querying                                [=========================]         
Finished                                [=========================]         
Package description
  package:       0ad-data-0.27.0-11.x86_64
  summary:       Cross-platform, 3D and historically-based real-time strategy game (data files)
  license:       GPL-2.0-or-later,CCPL
  group:         games
  download size: 1.4 GB (1,368,603,575 bytes)
  size:          3.5 GB (3,526,938,164 bytes)
  url:           https://play0ad.com
  description:   Cross-platform, 3D and historically-based real-time strategy game (data files)

[arrowd]

FWIW, this looks good to me.

[joebonrichie]

Partially superseded by 736585f

[ximion]

Right. To be honest, I really had thought we would be able to get rid of spawned backends (at least the generic support) - but now that we're getting another one, I guess that's not the case and we should make sure the current code works.

[joebonrichie]

Yeah the way spawned backends is architectured isn't my favourite tbh. If i gained a bunch of time it'll be interesting to experiment with other approaches. Cython may work. I know ikey was also experimenting with a varlink approach at some point. /offtopic

Anyway w.r.t the rest of the existing spawned backends do we just want to emit 2**64 - 1 (G_MAXUINT64) for the download-size property? It'll then correctly report as 'Unknown' in pkcon get-details for example.