Pass the current http.request to the _update_user backend hook

[devo-devo]

feat: Passes the current request to the _update_user hook.
This should allow developers, especially those dealing with multi-tenant sites, to make updates to the user based on the request context.
Closes #350

[devo-devo]

@peppelinux wondering what you're thinking of this? Not 100% sure what a could test for this would be.

[peppelinux]

you have also to add the argument request in the _update_user method, here
https://github.com/IdentityPython/djangosaml2/blob/master/djangosaml2/backends.py#L176

and also, please increase the release number here https://github.com/IdentityPython/djangosaml2/blob/master/setup.py#L30 to 1.5.4

please also change the titple of the PR and add a description about the scope of your contribution and the new feature that it introduce in the project

[devo-devo]

@peppelinux thank you for your notes! updated.

[peppelinux]

Please devo-devo, can you improve the documentation of djangosaml2, including this additional feature and a short description of your implementation use case and how you did it with the release we're going to make?

[devo-devo]

Will do asap!