A static or dynamic source of peer addresses.
These are used as fallbacks when we are bootstrapping and don't have a local cache, or when none of our addresses are functioning. Typically sources will represent things like static text in the config file, a separate local file with addresses, or a remote HTTPS URL that can be updated automatically. Another solution is to use a custom DNS server that hands out peer IP addresses when name lookups are performed.
Definition at line 37 of file Source.h.