Transport Log Level should be a CAP not Overwrite the Loggers Level

[martin-hartmond-mw]

winston-transport/index.js

Lines 74 to 78 in 7bbaf43

	// Remark: This has to be handled in the base transport now because we
	// cannot conditionally write to our pipe targets as stream. We always
	// prefer any explicit level set on the Transport itself falling back to
	// any level set on the parent.
	const level = this.level || (this.parent && this.parent.level);

This always overwrites the Logger Level.
The transports level should behave like a cap, so that the Developer can use the transport options to set global caps (e.g. don't log anything below WARN to the log server) while configuring context-specific levels in the loggers.

E.g.

transports: [
    FileTransport(level: VERBOSE),
    HttpTransport(level: WARN)
]
loggers: [
    Logger('application', level: INFO),
    Logger('redis', level: WARN),
    Logger('pgsql', level: VERBOSE),
]

I would expect SQL logs of 'psql' to show up only in the File Logs, and Redis debug messages to not show up at all. I would expect application info messages to show up in the File Logs only.

Related issue: the applicationinsights instrumentation of winston initializes the applicationinsights transport with 'silly', since it wants to log anything that the loggers deem log-worthy. This causes all debug logs to be transported into applicationinsights, no matter how the level on the specific logger is set.