installation: Flask-OAuthlib 0.6 upgrade

* Upgrades Flask-OAuthlib to v0.6.

* Adds '/' to the endpoints that need it in the test_provider.

* Uses the url_for in some functions in helpers testsuite in order to
  not hardcode the url.

* Fixes some PEP257 issues.

* NOTE require_api_auth no longer passes oauth request as view
  arguments. Instead user request.oauth to access oauth request.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
Reviewed-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
deposit: Flask-OAuthlib upgrade fix

* Fixes API changes related to Flask-OAuthlib upgrade.

* Some PEP257 love.

Co-authored-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
Reviewed-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
documents: Flask-OAuthlib upgrade fix

* Fixes API changes related to Flask-OAuthlib upgrade.

* Some PEP257 love.

Co-authored-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
Reviewed-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
webhooks: Flask-OAuthlib upgrade fix

* Fixes API changes related to Flask-OAuthlib upgrade.

* Some PEP257 love.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
Reviewed-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
tags: Flask-OAuthlib upgrade fix

* Fixes API changes related to Flask-OAuthlib upgrade.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
Reviewed-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>