Allow for the configuration to be sourced externally and updated at runtime

[dcoric]

Is your feature request related to a problem? Please describe.
Instead of a static proxy.config.json, we would like to have a way to provide the configuration from an external source (like a gitops repo, or an http service, etc.) and allow it to be reloaded/applied at runtime.

Describe the solution you'd like
The idea is to implement a robust remote configuration management solution for GitProxy that would support dynamic loading of configurations from multiple sources (local files, HTTP endpoints, and Git repositories). The system would maintain a default configuration in proxy.config.json which could be overridden by user-specific settings, and would feature a dynamic configuration loader that periodically checks for updates at configurable intervals. When changes are detected, the system would validate the new configuration, gracefully stop existing services, apply the updates, and restart services with the new configuration. The solution would include built-in error handling with automatic rollback to previous configurations if updates fail, and would provide an admin-only endpoint for manual configuration reloading. This architecture would ensure that configuration changes could be managed centrally while maintaining system stability and availability, with the ability to merge configurations from multiple sources when needed.

Describe alternatives you've considered
None

Additional context
The idea behind remote configuration management for GitProxy is to enable automated, remote configuration updates without requiring manual intervention or service restarts. This would allow administrators to centrally manage and update configurations across multiple GitProxy instances, ensuring consistent settings and reducing operational overhead. The system would automatically detect and apply configuration changes from remote sources while maintaining system stability through validation and rollback capabilities.