Remove FKs before initial sync and recreate after initial sync

See merge request !124

Enabled concurrent flush of Follow objects.

Fixes around post data edit

See merge request !120

Fixed edit case with empty title, body or json_metadata
Fixed use of json - now everywhere ujson is used
In case json_metadata in comment_operation would not actually be json, HiveMind no longer crashes on access
Since we are handling bad json anyway it was no longer needed to fill empty json_metadata with {}, original empty string restored

Avoiding a redundant loop during `effective_comment_vote_operation` processing

See merge request !116

Teh call `get_profile` works

See merge request !110

Some characters apparently need long 8-byte encoding

See merge request !117

[ABW]: some characters apparently need long 8-byte encoding (problem actually caused by use of ujson)

Unified some error messages and added CI groups for tests made in new scheme

See merge request !114

added new test groups to CI with at least single test to make it easier to move tests accourding to new scheme (only follow/tags have no negative tests so no such groups were added)

Database api fixes

See merge request !103

fixed unicode escaping

See merge request !113

[ABW]: added separate tests to CI (all tests will eventually be run through folders instead of common .yaml file)

Add num_block to tables, add proper reblog support

See merge request !112