Code review comment for ~pelpsi/launchpad:social-account-interface-and-implementation

> We need to find a way to define how the JSON for a platform should look like
> (since some platforms will require only a nickname, and others will require
> nick + network, and eventually we might have even more complex schemas).
>
> I'm wondering where we should add that, but I feel like it should perhaps be
> somewhere in the `PlatformType` class

I am not a fan of using the IRC-specific (or specific to few platforms) naming conventions for other services like Matrix. Matrix user IDs (MXID) use the format '@<email address hidden>' (see https://matrix.org/docs/older/faq/). So I would prefer using similar naming here - username and homeserver. It is better to store those separately instead of as an MXID because it will be easier to query accounts on a specific homeserver.