* refactor: improve error handling
* fix: specify bind address instead of port
* fix: remove temporary testing file
* fix(errors): change error names to snake_case
* refactor(errors): split indexing error types, remove unused errors
* feat: add env variable checking at program start
This just checks whether the enviroment variables exist and can
parse to the given type and gives a warning if they can't. This
should prevent cases where the program fails at runtime due to
checking an environment variable that doesn't exist.
