Logger dependency

[René Terstegen]

The bundle uses the monolog.logger service which is not a requirement of in composer.

[René Terstegen]

Default logger is set to the NullLogger of the psr\log package. A logger can be defined by creating a bnnvara_graphql.yaml config file and adding the following content:

    bnnvara_graphql:
        logger_service: monolog.logger

In this example the monolog.logger is used, but all loggers implementing the psr standard can be used.