.terraformrc

Provider Cache Server now supports custom host blocks

Running terragrunt with the Provider Cache Server enabled against a private registry declared via a host block in .terraformrc (or a file referenced by TF_CLI_CONFIG_FILE) failed with errors such as provider registry.opentofu.org/<org>/<provider> was not found, because the cache server proxy did not recognize the custom registry and rewrote requests to registry.opentofu.org.

Terragrunt now registers each custom host block with the cache server, seeds its service discovery from the services map so registries that do not serve .well-known/terraform.json still work, and forwards OPENTOFU_NETRC_* / TF_TOKEN_* credentials so authenticated registries continue to authenticate through the proxy.

# .terraformrc
host "registry.example.com" {
  services = {
    "providers.v1" = "https://registry.example.com/repository/terraform-hosted/v1/providers/"
  }
}

Resolves #5916. Thanks to @elkh510 for contributing this fix!