About

As discussed in #17, we would like to have a way for configuring some application-wide settings through a configuration file.

Solution

We will use a 2-level configuration. Any given setting will be first read from a configuration file, if the configuration file does not exist or does not specify the desired setting, a sensible default should be used.
The configuration file will be in JSON format.
The file location is pre-defined, and varies based on operating system:

• Linux: we'll follow the XDG spec and the file will be placed at $XDG_CONFIG_HOME/icm/settings.json. $HOME/.config will be used in place of XDG_CONFIG_HOME if it is not set.
• MacOS: I could not find any official up-to-date documents, but archived documents suggest we should place our file at $HOME/Library/Application Support/icm/settings.json. I found other people corroborating the information and no suggestion of alternative locations.
• Windows: I could not find any official documents, but the overall consensus on the internet is that application configuration files should be placed within "%AppData%", so we'll use %AppData%\icm\settings.json

The implementation can use the two variables we already wish to parameterize (HTTP server host and port) to provide a more complete feature and better validate itself.

This issue does not cover features for manipulating the settings file.