Abstract authenticator #4985

Job	Run time
Compile LavinMQ	56s
Format check	14s
Spec FreeBSD	3m 34s
Lint check	1m 1s
Lint OpenAPI	17s
Lint javascript	15s
Filters for frontend specs	5s
Spec	2m 3s
Spec OS X	2m 38s
RabbitMQ java client test	5m 1s
RabbitMQ HTTP API Ruby client test	1m 6s
Bunny client test	2m 39s
RabbitMQ HTTP API Go client test	59s
Test in release mode	20s
Frontend specs	0s
	21m 8s

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