for verbose log messages for development or debugging only, as bitcoind may run
more slowly, that are more granular/frequent than the Debug log level, i.e. for
very high-frequency, low-level messages to be logged distinctly from
higher-level, less-frequent debug logging that could still be usable in production.
An example would be to log higher-level peer events (connection, disconnection,
misbehavior, eviction) as Debug, versus Trace for low-level, high-volume p2p
messages in the BCLog::NET category. This will enable the user to log only the
former without the latter, in order to focus on high-level peer management events.
With respect to the name, "trace" is suggested as the most granular level
in resources like the following:
- https://sematext.com/blog/logging-levels
- https://howtodoinjava.com/log4j2/logging-levels
Update the test framework and add test coverage.
Add a regression test for https://github.com/bitcoin/bitcoin/pull/21407.
The test creates a socket that, upon read, returns some data, but never
the expected terminator `\n`, injects that socket into the I2P code and
expects `i2p::sam::Session::Connect()` to fail, printing a specific
error message to the log.
