This follows the same flows-based flow as regular registration, but as
the only implemented flow has no requirements, it auto-succeeds. In the
future, other flows (e.g. captcha) may be required, so clients should
treat this like the regular registration flow choices.
SYN-287
This requires that HS owners either opt in or out of stats reporting.
When --generate-config is passed, --report-stats must be specified
If an already-generated config is used, and doesn't have the
report_stats key, it is requested to be set.
This just replaces random bytes with macaroons. The macaroons are not
inspected by the client or server.
In particular, they claim to have an expiry time, but nothing verifies
that they have not expired.
Follow-up commits will actually enforce the expiration, and allow for
token refresh.
See https://bit.ly/matrix-auth for more information
