We previously covered everything about using providers on a single page,
but that was getting unwieldy already and we now have a lot more to
discuss with v0.13 introducing a new source address syntax and some other
concepts.
Here we split the provider-related content into two parts: "Provider
Requirements" covers how to find and declare dependencies on providers,
and then "Provider Configuration" (formerly just "Providers") then focuses
primarily on how to write zero or more provider configurations for a
particular provider.
Because "Provider Requirements" is now presented before "Provider
Configuration" in the navigation, I've also moved some of the introductory
content about providers in general onto the "Requirements" page. The
first paragraph of that content is duplicated onto the "Configuration"
page for discoverability, but we now link to the requirements page to get
the full story.