Added OIDC support, improved OAuth flow

[epiclen]

Added code to support Dex based authentication.

[squash-labs]

Manage this branch in Squash

Test this branch here: https://epiclentestlink-1-9-52oru.squash.io

[fmancardi]

Hi:
would you mind providing some documentation regarding configuration?
also, instructions to set a testing environment will be great

[epiclen]

Hey @fmancardi
I added dex.md to describe how to configurate dex oauth.

[fmancardi]

Thanks.
I know absolutely ZERO about DEX, then my question is:
there is some ONLINE Free server that can be used to test your implementation, the same way I can test OAuth with Microsoft, Azure, Google, Github?
I would like to do some tests before adding to stable code
thanks again

[epiclen]

Dex is an identity service that uses OpenID Connect to drive authentication for other apps.
It`s usually uses to provide private authentication service.There is no public server.
https://github.com/dexidp/dex

[danielfbm]

I understand that Dex mostly provides OpenID Connect authentication, so would this feature be able to use other OIDC providers like Keycloak, Auth0? If yes, can you do some quick testing using Auth0, maybe write down here the steps you took to test.

If it works for other OIDC providers, I believe is best to make it as an OIDC authentication mechanism, and not a vendor specific

[epiclen]

@danielfbm
Sorry,this is my fault.As you say,"Dex mostly provides OpenID Connect authentication".It is not only support dex.
Dex is an identity service that uses OpenID Connect to drive authentication for other apps.
This pr actually add OpenID Connect support.
@fmancardi This feature also work with other oidc provider.