svchost/auth: HostCredentialsFromMap function
svchost/auth: HostCredentialsFromMap function

This function deals with turning a map derived from some user input
(e.g. in a config file) into a HostCredentials object, if possible. This
will be used as a standard way to specify credentials so we have a place
to add new credentials types in future and have support for those across
all of our map-based CredentialsSources.

hashicorp/terraform-plugin-sdk,hashicorp/terraform-plugin-sdk