Document & enforce valid characters for all configuration #768
Description
It would be exceptionally useful to document the valid characters for all configurations of SAP (e.g., long & short flag names, long & short option names, command names, etc.), and enforce rejection of all invalid characters in one central location.
This will:
- prevent different parts of SAP from expecting different sets of valid characters for the same values
- simplify shell completion script generation
- prevent bugs