Remove delivery_tag and delivery_tag_pool fields from conversation model and fix/kill everything that looked at them.
Fix dialogue test cases that were broken because they alway fails on my machine and I failed to notice that the failure was different.
Merge branch 'develop' into feature/issue-624-clean-up-conversation-model
Merge branch 'develop' into feature/issue-624-clean-up-conversation-model
Turn the Conversation model "batches" field into a mandatory "batch" field.
Fix docstring.
Handle newer conversation versions better in migration command.
Cosmetic fixes and better error message for batch-related migration failure.
Merge branch 'feature/issue-624-clean-up-conversation-model' into develop