add configurable service root to oauth config

[aukeman]

In the oauth2 configuration, add a new config item service_root which will be used as the path for the 302 redirection to the application upon authentication by the service provider.

This value will default to /, so existing behavior will be unchanged.

This will allow for oauth to be used in installations where the application is not served directly from the root path

Also, mod.go was modified when building so I checked it in. This does not affect my change so I can revert that if you'd like

[CLAassistant]

All committers have signed the CLA.

[adubovikov]

Thank you! Can you please sign the CLA ?

[aukeman]

Since I made the contribution as part of my work I would like to get the ok from my employer's legal department first. Doesn't look to me like there's anything that would be a problem but you know how it goes. Will sign just as soon as they clear it.

[aukeman]

Thank you! Can you please sign the CLA ?

all done. once merged, any chance we can get a release with this change? thanks

[lmangani]

Thanks @aukeman and yes, new builds are immediately available on github and ghcr.io

[lmangani]

@aukeman homer-app-1.4.44