Functions to resolve and call a Summon provider.
func Resolve(providerArg string) (string, error)
Searches for a provider in this order:
providerArg, passed in via CLI- Environment variable
SUMMON_PROVIDER - Executable in
/usr/libexec/summon/.
func Call(provider, specPath string) (string, error)
Given a provider and secret's namespace, runs the provider to resolve the secret's value.