Constrain Default LogLevel

[phptek]

If user's don't modify their project's reporting levels, then the module defaults to the most verbose reporting level (Logger::Debug) which has deleterious effects on data-storage requirements of aggregation backends.

In order to ascertain how best to patch this, we need to get an idea of how the upstream sentry/sentry package treats configured severities e.g. given a project configured with INFO which is correct?

a). Only sends INFO messages to Sentry
b). Sends INFO + (And above) messages to Sentry

See:

silverstripe-sentry/src/Adaptor/SentrySeverity.php

Line 51 in 223d540

public static function from_error(string $severity): string

This ticket therefore covers the following:

1. Fix areas of SentryHandler and SentryLogger which don't appear to consume the configured level when reporting exceptions (messaging is OK)
2. Modify Monolog\Logger::DEBUG to Monolog\Level::Warning
3. Constrain the default in SentryLogger::factory() to use Monolog\Level::Warning
4. Modify examples and docs to encourage use of Warning+