Split query#available_filter_options and move into mix in
Rename query#available_filters
Introduce query filter objects (WIP)
Add query filter validations, validate values of filters of integer type
Validate presence of query filter field, remove obsolete attribute accessor
Forward filter error messages to query
Add presence of query filter field validation spec
Avoid duplicate work package query filters
Fix work package steps with regard to query filters
Fix query unit tests
Fix error message assertion when query filter cannot be blank
Move query filter-related code to models/query because it existed first
Move filter types by fields concerning work packages to corresponding filter subclass
Stringify keys of serialized filter hashes


This ensures backwards code compatibility. Can be reverted for aesthetic reasons later on.
Only initialize queries with status filters if no filters have been selected by user
Validate presence of query filters
Ensure valid setup of queries from factory
Fix work packages controller spec after changing the query default filter setup
Fix unit tests after changing the default query filter setup
Fix query integration test after changing the default query filter setup