This adds support for syncing ownership on Unixes and on Windows. The
scanner always picks up ownership information, but it is not applied
unless the new folder option "Sync Ownership" is set.
Ownership data is stored in a new FileInfo field called "platform data". This
is intended to hold further platform-specific data in the future
(specifically, extended attributes), which is why the whole design is a
bit overkill for just ownership.
This makes us use TLS 1.3+ on sync connections by default. A new option
`insecureAllowOldTLSVersions` exists to allow communication with TLS
1.2-only clients (roughly Syncthing 1.2.2 and older). Even with that
option set you get a slightly simplified setup, with the cipher suite
order fixed instead of auto detected.
This adds two new configuration options:
// The number of connections at which we stop trying to connect to more
// devices, zero meaning no limit. Does not affect incoming connections.
ConnectionLimitEnough int
// The maximum number of connections which we will allow in total, zero
// meaning no limit. Affects incoming connections and prevents
// attempting outgoing connections.
ConnectionLimitMax int
These can be used to limit the number of concurrent connections in
various ways.
