Defaults: Generate environment fallbacks

[QuintinWillison]

Generic Specification

Per RSC15g, introduced in ably/docs#965.

See ably/ably-js#682 and ably/ably-ruby#196 for reference implementations.

Flutter Specific Notes

Given this client library is a plugin (i.e. delegates most of its work to native implementations), I'm not sure how much work is required to to make this happen as the majority (if not all) of the work to complete this may be required to be completed in the upstream native dependencies via:

• Defaults: Generate environment fallbacks ably-cocoa#1066
• Defaults: Generate environment fallbacks ably-java#603

┆Issue is synchronized with this Jira Story by Unito

[tiholic]

@QuintinWillison Yes, only change to be handled is to deprecate fallbackHostsUseDefault

[ably-sync-bot]

➤ Jamie Newcomb commented:

Rohit R. Abbadi can you look at this next please

[QuintinWillison]

We need to look at whether any work is required before we can safely close this issue.

[ikurek]

@QuintinWillison I think it was done as a side-effect of #69 in commit 4d21e7c, the @deprecated annotation was added on fallbackHostsUseDefault field. I don't think there's anything more we have to do with this, since the rest seems to be handled by java and cocoa libs, so I'm closing this for now