Add specs
Remove custom field from cost query on delete
Destroy custom field after removal from cost query
Add session spec
Remove custom field from query in session
Require group-bys to fix object resolution
Merge pull request #45 from finnlabs/stable_fix/7905_custom_field_not_removed_from_cost_report_after_delete

7905 custom field not removed from cost report after delete
Update CHANGELOG.md
Bump version to 3.0.8

Due to our (new) convention plugins inherit their versions from the
OpenProject core. The next stable release of the OpenProject core is
3.0.8.
Update stable to v3.0.8