* started chat model
* refactor processing commands and UI events
* message chat event processing
* groups: delayed delivery of messages and introductions to announced members (#217)
* combine migrations, rename fields
* show all view messages vis ChatResponse type
* serialize chat response
* update C api
* remove unused extensions, fix typos
Co-authored-by: Efim Poberezkin <8711996+efim-poberezkin@users.noreply.github.com>
