OAuth: Introduce new setting for configuring max age of OAuth state cookie

[rtrompier]

When using oauth2 authentication with multifactor, the 60s delay may be too short

[CLAassistant]

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[papagian]

Thank you for contributing!
Instead of a new hardcoded value would you like to introduce a new setting oauth_state_cookie_max_age that defaults to 60?

For doing so, in addition to this modification when writing the OAuth state cookie, you need to update appropriately defaults.ini, samples.ini and the docs.

[rtrompier]

Hi @papagian,

I work for the Geneva Hospitals, and we are currently using grafana for COVID19 crisis monitoring. Would it be possible to merge in the state although I agree with you that it would be more elegant via a configuration file ?

Thank you very much ;)

[aknuds1]

LGTM!

[papagian]

@rtrompier
I have introduced the new setting. You can override the default behaviour by setting oauth_state_cookie_max_age (under auth section) to 500 in your grafana configuration or alternatively by using the environmental variable GF_AUTH_OAUTH_STATE_COOKIE_MAX_AGE=500.

Stay strong and let me know if you need additional help.

[rtrompier]

Thank you so much guys !
Really appreciate your help.