accesslog - porting accesslogs capabilities from DT's gateway

[pmauduit]

Somehow relates to https://github.com/georchestra/georchestra-gateway/issues/112

This work has been done on the DT fork but not ported here yet.

TODO:

• Adding documentation ; DT is making use of JSON format, I think we can have something as JSON or closer to what is expected in #112 with only changes in the logging configuration, making everyone happy. Note that the -Dreactor.netty.http.server.accessLogEnabled=true should also be documented
• One test related to rabbitmq event emission is failing, because it expects an output from the console testcontainer, which somehow does not work with the modified logging configuration. There might be something more relevant than parsing the container output as test result, but not sure of what could be a better approach yet.

[pmauduit]

• One test related to rabbitmq event emission is failing

maybe the test should go into the console testsuite instead of here ?