Trogon.Configurable
Trogon.Configurable gives an Elixir module one place to read its configuration from. A single use line adds a get_config/1 function that returns a keyword list.
The function merges three sources, where each one overrides the one before it. The defaults passed to use come first, then the module's entry in its OTP app environment when an otp_app is given, and finally the options passed to get_config/1 at the call site.
Modules that read configuration from more than one place tend to reimplement the same merge, each with its own precedence. One module lets the call site win, another lets the environment win, and a value that works in one place silently loses in the next. Fixing the precedence in one package keeps defaults next to the code, lets each environment swap values through Config, and still lets a caller adjust a value for a single call.
This is for Elixir developers writing libraries or application modules that need sensible defaults which an application, or a single call, can override. Clients for external services, adapters, and workers that read endpoints, timeouts, or credentials are typical examples.