Fix and add warning for duplicate logger context names

[joshdover]

By default, Kibana plugins are provided with a Logger instance that is already configured with a context name of the format plugins.<pluginId>. However, some plugins are creating child loggers that ALSO add the plugin's ID, resulting in a context like plugins.<pluginId>.<pluginId>.

This is unnecessary and should be removed. Here are some plugins currently doing this:

• taskManager (@elastic/kibana-alerting-services):

  kibana/x-pack/plugins/task_manager/server/plugin.ts

  Line 58 in eee1392

  const logger = this.initContext.logger.get('taskManager');

• securitySolution (@elastic/siem): https://github.com/elastic/kibana/blob/master/x-pack/plugins/security_solution/server/plugin.ts#L126

First, we should definitely fix the offending plugins. But second, we could improve the developer experience here by logging a warning (in development?) when a logger.getLogger is called with a consecutive duplicate context name.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

by logging a warning (in development?) when a logger.getLogger is called with a consecutive duplicate context name.

+1 for only logging in dev mode.

[mikecote]

Thanks for the heads up, we did the fix in taskManager

kibana/x-pack/plugins/task_manager/server/plugin.ts

Line 40 in 5460ad7

this.logger = initContext.logger.get();