This is transient file that lists functionalities to be implemented before
first major release.

- autocomplete: don't show items that are already used in tag list (unsure)
- posts/upload: ability to paste many urls (unsure)
- posts/listing: add buttons for toggling safety
- users: add user-configurable "about me" (should support Markdown)
- tags: add tag merging
- tags: add tag descriptions
- tags: add tag edit snapshots (backed-only)
- add /history

refactors:
    - add enum validation in IValidatables (needs refactors of enums and
      possible disposal of EnumHelper in favor of something more subtle)
    - reduce dependencies
    - split PostService into PostSearchService and PostEditService