Add a redirect flow for end_session endpoint handling

[arssly]

I've added a redirect flow for handling the end_session endpoint. end session flow is much like the auth flow. so in order to avoid duplicate code, I used a base class for both end_session and auth flow.

[guillaume-chervet]

Is there any chance for this PullRequest to be merged? :)

[bonnetb]

Hi, we really need this feature : having a clean logout is mandatory for enterprise apps. Could you merge this PR, please ?

[guillaume-chervet]

Do you have any news ?

[guillaume-chervet]

Any chance for a merge?

[allemas]

Hi, we need this PR to fix a bug in our application. Any chance for a merge?

[abatovua]

Need this feature. Any updates?

[guillaume-chervet]

Me too, do you need any help?

[tielushko]

Please, are there any updates on the merge?

[tielushko]

@tikurahul @Meligy

[guillaume-chervet]

@arssly ?

[TeckTn]

Any chance that this pr get merged ?