Loads the credential by auth config and current tool context from the backend credential store.
The auth config which contains the auth scheme and auth credential information. auth_config.get_credential_key will be used to build the key to load the credential.
The context of the current invocation when the tool is trying to load the credential.
A promise that resolves to the credential saved in the store.
Abstract class for Service that loads / saves tool credentials from / to the backend credential store.