Fix extension for file download in styles

[boney-bun]

fix #536

[boney-bun]

tested on safari, chrome and firefox.

the PR in action using safari:

@lucernae i've tried the content_type of application/xml, but safari still automatically adding xml extention to the filename. so i define content_type of text/vnd.qt.qml for qml file.
found this content type here: https://www.ietf.org/mail-archive/web/media-types/current/msg00465.html

@gubuntu @NyakudyaA can text/vnd.qt.qml be used to define qml file in content type?

[gubuntu]

afaik Qt-QML is a completely different animal.

though if it serves to add the .qml suffix maybe it is OK?

[codecov]

Codecov Report

Merging #541 into 2.8.x-qgis_server will decrease coverage by 7.95%.
The diff coverage is n/a.

@@                  Coverage Diff                  @@
##           2.8.x-qgis_server     #541      +/-   ##
=====================================================
- Coverage              41.52%   33.56%   -7.96%     
=====================================================
  Files                    412      412              
  Lines                  29670    29670              
  Branches                3752     3752              
=====================================================
- Hits                   12319     9958    -2361     
- Misses                 16589    19083    +2494     
+ Partials                 762      629     -133

Impacted Files	Coverage Δ
geonode/qgis_server/views.py	0% <ø> (-60.42%)	⬇️
geonode/qgis_server/context_processors.py	0% <0%> (-100%)	⬇️
geonode/qgis_server/urls.py	0% <0%> (-100%)	⬇️
...ent/commands/delete_orphaned_qgis_server_layers.py	0% <0%> (-100%)	⬇️
geonode/qgis_server/tests/test_qgis_settings.py	0% <0%> (-100%)	⬇️
geonode/qgis_server/tests/test_xml_utilities.py	0% <0%> (-100%)	⬇️
.../qgis_server/migrations/0003_auto_20170727_0509.py	0% <0%> (-100%)	⬇️
.../qgis_server/migrations/0005_auto_20170823_0341.py	0% <0%> (-100%)	⬇️
geonode/qgis_server/migrations/0001_initial.py	0% <0%> (-100%)	⬇️
geonode/qgis_server/admin/__init__.py	0% <0%> (-100%)	⬇️
... and 48 more

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[codecov]

Codecov Report

Merging #541 into 2.8.x-qgis_server will not change coverage.
The diff coverage is 100%.

@@                Coverage Diff                 @@
##           2.8.x-qgis_server     #541   +/-   ##
==================================================
  Coverage              41.52%   41.52%           
==================================================
  Files                    412      412           
  Lines                  29670    29670           
  Branches                3752     3752           
==================================================
  Hits                   12319    12319           
  Misses                 16589    16589           
  Partials                 762      762

Impacted Files	Coverage Δ
geonode/qgis_server/views.py	60.41% <ø> (ø)	⬆️
geonode/qgis_server/tests/test_views.py	99.28% <100%> (ø)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[gubuntu]

@boney-bun respond and fix

[lucernae]

LGTM, thanks @boney-bun !

I think this is fairly straightforward PR.

[lucernae]

For @gubuntu 's and @boney-bun 's comment:

@lucernae i've tried the content_type of application/xml, but safari still automatically adding xml extention to the filename. so i define content_type of text/vnd.qt.qml for qml file.
found this content type here: https://www.ietf.org/mail-archive/web/media-types/current/msg00465.html

The original mime type follows from QGIS definition taken here:
https://github.com/qgis/QGIS/blob/master/rpm/sources/qgis-mime.xml

There should be a way to force Safari to save the filename with QML extension (with mime type application/xml). This can be from Javascript file, communicated in the request header, or from download attribute.

afaik Qt-QML is a completely different animal. though if it serves to add the .qml suffix maybe it is OK?

Yes, I think this is last resort though. If above suggestion still not feasible :(.