Require agents specified by ClientOptions#agents to have a version

[lawrence-forooghian]

This comes from a conversation I had with Quintin about trying to figure out the best way to represent “this agent has no version” in Objective-C, where a dictionary cannot contain a nil value.

He suggested that it would be best to simply remove this scenario by requiring a version, since the #agents property is only for use by other Ably SDKs (as already made explicit by RSC7d6b), which will always have a version.

[owenpearson]

It doesn't logically follow from RSC7d6b that the Ably authored SDK won't ever have a requirement to append an unversioned agent. I think your point in the PR description assumes that the SDKs using this option will only ever use it to represent themselves which I don't think is a safe assumption (even if it's probably true for all SDKs currently).

If objective-c doesn't allow dictionaries with nil values is there not something like the rust Option type that we can use instead?

[lawrence-forooghian]

I think your point in the PR description assumes that the SDKs using this option will only ever use it to represent themselves which I don't think is a safe assumption

That's a very good point.

If objective-c doesn't allow dictionaries with nil values is there not something like…

Yep, there are definitely ways that we can get around it, I just went with the spec change because it was what Quintin was leaning towards, but I think given your point above it makes more sense for me to address this at the ably-cocoa level. Gonna put this back into draft and remove reviewers whilst I think about it. Thanks for your input!

[lawrence-forooghian]

Closing this one.