Drop the requirement to set a provider when setting config/secrets through the controller and there's only one provider

[alecthomas]

eg. in production there's (currently) only ASM/DB, so it's redundant to have to specify --asm

Instead the cluster would be required to start with a flag specifying the writing resolve, so the client would not make any decisions.

This change should allow the controller to support multiple providers for reading but only one for writing, as usual, but the controller is the one that selects the writer at startup. This would also remove the types for setting the provider over gRPC. The client will still need these flags for the local case, but for the gRPC path it would be able to skip requiring the user to set a writer.

[jonathanj-square]

@alecthomas I am not clear on "Instead the cluster would be required to start with a flag specifying the writing resolve, so the client would not make any decisions." - my best guess is...

The cluster needs to expose a flag to determine which config / secret provider to use as default, in the event that there are multiple, so the client is never required to supply a provider when setting a config or secret. Is that anywhere near what you meant?

[alecthomas]

That's exactly correct. Instead of the client controlling what writer to use, the controller does.

[alecthomas]

This is not high priority though, let me remove it from next.

[alecthomas]

Actually let's do some prioritisation in the sync today.

[alecthomas]

@jonathanj-square I'm going to include this in some general config refactoring I'm doing