The ephemeral manager keep the inactive ephemeral peers in a linked list. The manager schedule a cleanup procedure to the head of the linked list (to the most deprecated peer). At the end of cleanup schedule the next cleanup to the new head.
If a device connect back to the server the manager will remote it from the peers list.
With this fix, all nested slices and pointers will be copied by value.
Also, this fixes tests to compare the original and copy account by their
values by marshaling them to JSON strings.
Before that, they were copying the pointers that also passed the simple `=` compassion
(as the addresses match).
This PR adds system activity tracking.
The management service records events like
add/remove peer, group, rule, route, etc.
The activity events are stored in the SQLite event store
and can be queried by the HTTP API.
Add a usage_limit parameter to the API.
This limits the number of times a setup key
can be used.
usage_limit == 0 indicates the the usage is inlimited.
