Replace ban text with localizable message

[](https://issuehunt.io/r/FAForever/server/issues/640)

The server should not be sending any strings that get rendered in the client, because these strings are in English and we can't be sure that the user on the other end has their client set to English (in fact a majority of people probably knows English only as a second language, or does not know it very well at all). In fact issue #444 already covers this, but I'm making another ticket just for this message because changing it would allow us to drop the `humanize` dependency.

Here is a link to the message:
https://github.com/FAForever/server/blob/e4ca993a9b7ea8123c64f6917bf9edd05f69b0ce/server/lobbyconnection.py#L1094

It should be replaced with something like:
```
{
"command": "banned",
"expires_at":
}
```

See #183 for inspiration, but note that we should be sending ISO timestamps (in UTC) and not timedeltas.

---

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