@spec fetch(t(), atom()) :: {:ok, any()} | {:error, Assent.Config.MissingKeyError.t()}

Fetches the key value from the configuration.

See Keyword.get/3.

@spec json_library(t()) :: module()

Fetches the JSON library in config.

If not found in provided config, this will attempt to load the JSON library from global application environment for :assent. Defaults to Jason.

See Keyword.merge/2.

See Keyword.put/3.