Add a user role which gets all required default permissions

[JNKielmann]

This PR implements a new default role "roles/user" which is created on system initialization. This role should get permissions that every user needs by default and is assigned to new users on creation. This will make it easier to add new default permissions on an already installed ML Lab instance, as only the role needs to be adjusted.

Additionally, a new helper function auth_utils.create_and_setup_user was added which performs user creation and setup (assign user role and create user's home project). This way user creation and setup is always done immediately together.

[lgtm-com[bot]]

This pull request introduces 1 alert when merging d6b6778845c1ecb2fff330d4549339d0e4809971 into 047f10c72744873ef1b0068706f131203c524635 - view on LGTM.com

new alerts:

• 1 for Polynomial regular expression used on uncontrolled data

[lgtm-com[bot]]

This pull request introduces 1 alert when merging 2fb4b5b1fef01d0124e2db962f76bda7f150a8e1 into 047f10c72744873ef1b0068706f131203c524635 - view on LGTM.com

new alerts:

• 1 for Polynomial regular expression used on uncontrolled data