We've run into a few cases where we need to change a configuration option for coder server. This can be particularly dangerous when users upgrade as it could change the deployment/security of their deployment as soon as they upgrade.

• fix: Allow overriding env variable names, restore CODER_TELEMETRY #4894
• feat: Allow multiple OIDC domains #5210
• feat: allow all GitHub login when no org is set #4837

In the case of #5210, we probably could always support the following as aliases: CODER_OIDC_EMAIL_DOMAIN, CODER_OIDC_EMAIL_DOMAINS. Perhaps with viper aliases?

However, there may be cases where we entirely rename a variable or change its configuration format. We could support the old format for a while, but notify the admin to use the new format via server logs and on the deployment page (as it may be removed in a future version).