* internal/registry source: return error if requested provider version protocols are not supported
* getproviders: move responsibility for protocol compatibility checks into the registry client
The original implementation had the providercache checking the provider
metadata for protocol compatibility, but this is only relevant for the
registry source so it made more sense to move the logic into
getproviders.
This also addresses an issue where we were pulling the metadata for
every provider version until we found one that was supported. I've
extended the registry client to unmarshal the protocols in
`ProviderVersions` so we can filter through that list, instead of
pulling each version's metadata.
We previously had only a stub implementation for a totally-empty
MultiSource. Here we have an initial implementation of the full
functionality, which we'll need to support "terraform init -plugin-dir=..."
in a subsequent commit.
Our existing provider installer was originally built to work with
releases.hashicorp.com and later retrofitted to talk to the official
Terraform Registry. It also assumes a flat namespace of providers.
We're starting a new one here, copying and adapting code from the old one
as necessary, so that we can build out this new API while retaining all
of the existing functionality and then cut over to this new implementation
in a later step.
Here we're creating a foundational component for the new installer, which
is a mechanism to query for the available versions and download locations
of a particular provider.
Subsequent commits in this package will introduce other Source
implementations for installing from network and filesystem mirrors.
Kristin Laemmert