tst_oauth2 and tst_deviceflow have many things in common, but sharing them is not trivial, or more aptly put, results in messy autotest code with a lot of if/elses.

However the test cases should be finegroomed if more can be shared. Possibly a new tst_authorizationcodeflow test should be introduced, and the tst_oauth2 should just focus on testing abstract oauth2 setters.

Without such refactorings, the autotests are (increasingly) hard to maintain, and contain unnecessary duplication and work effort in the long term.