@spec get(atom(), atom(), term() | nil) :: term()

Fetches a value from the config, or from the environment if {:system, "VAR"} is provided.

An optional default value can be provided if desired.

Example

iex> {test_var, expected_value} = System.get_env |> Enum.take(1) |> List.first
...> Application.put_env(:myapp, :test_var, {:system, test_var})
...> ^expected_value = Elixir.ExGram.Config.get(:myapp, :test_var)
...> :ok
:ok

iex> Application.put_env(:myapp, :test_var2, 1)
...> 1 = Elixir.ExGram.Config.get(:myapp, :test_var2)
1

iex> :default = Elixir.ExGram.Config.get(:myapp, :missing_var, :default)
:default

@spec get_integer(atom(), atom(), integer() | nil) :: integer()

Same as get/3, but returns the result as an integer. If the value cannot be converted to an integer, the default is returned instead.