CKAN 2.10 support

[pdelboca]

This PR adds CKAN 2.10 support to the extension.

Main changes

• CKAN 2.10 refactors the activity stream logic into it's own core extension. Therefore we need to change where we import from based on the version we are running.
• setup() method in tests is no longer recommended so I extracted it as a fixture. It also was failing, check the migration wiki for more info: https://github.com/ckan/ckan/wiki/CKAN-2.9-to-2.10-migration-tips#test-classes-setup-methods-not-firing-or-firing-in-wrong-order

[codecov-commenter]

Codecov Report

Merging #48 (fb7a97d) into main (3a6094a) will increase coverage by 0.21%.
The diff coverage is 93.22%.

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
+ Coverage   66.98%   67.20%   +0.21%     
==========================================
  Files          15       15              
  Lines        1054     1061       +7     
==========================================
+ Hits          706      713       +7     
  Misses        348      348              

Impacted Files	Coverage Δ
ckanext/versions/logic/action.py	71.90% <55.55%> (+0.47%)	⬆️
ckanext/versions/tests/test_actions.py	99.00% <100.00%> (ø)
ckanext/versions/tests/test_auth.py	100.00% <100.00%> (ø)

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