Runtime plugin configuration for DurableState

[ptrdom]

Just like with EventSourcedBehavior, it would be useful if runtime plugin configuration was possible for DurableState.

apache/pekko-persistence-r2dbc#194 adds the implementation for R2DBC plugin.

[pjfanning]

@ptrdom Would you be able to provide a little more detail on which parts of the 194 PR that you think should be copied into this repo?

[ptrdom]

I think nothing will need to be copied into this repo from 194 PR, just that once this repo implements necessary changes for plugin interface then users will be able to use the plugin implementation from 194 PR.

Necessary changes will likely be, at the very least, to the DurableStateBehavior interface to allow setting the runtime config, then DurableStateStoreRegistry will need a new method to allow passing that config further to the plugin implementations.

[pjfanning]

presumably something a bit like #1518

[ptrdom]

Yes, very similar indeed.