Import (some?) definitions after enabling plugins

[michaelklishin]

See rabbitmq/rabbitmq-shovel#13 for background.

Definition import was moved into the core but we still perform it before enabling plugins. I wonder if this should be the other way around. Admittedly there's a chicken-and-egg problem here either way: plugins can potentially depend on definitions (e.g. policies and parameters) and definitions can depend on plugins.

We can introduce a separate "delayed import" setting for definitions that depend on plugins being enabled.

[lukebakken]

@michaelklishin it seems that this issue is related - rabbitmq/rabbitmq-sharding#39

[michaelklishin]

Addressed in #2384.

[michaelklishin]

Addressed in #2384 which will ship in 3.8.6. Those on earlier versions can always import definitions after node startup.

[ebuildy]

Do you know when the bug appears? its working fine with 3.7.8

[lukebakken]

RabbitMQ version 3.8.4.

[michaelklishin]

It's not new in 3.8.4 but it affects more plugin types as of 3.8.4 because boot code paths have been substantially refactored.