the provider details tests were previously very stateful - they
would update a value, and then because provider_details is a "static"
table that is not wiped by the notify_db_session fixture, the tests
were forced to make a second update that reverted that change. if the
test fails for whatever reason, the provider_details table ends up
permanently modified, playing havoc on tests further down the line.
this commit adds the fixture `restore_provider_details` to conftest.
this fixture stores a copy of the contents of ProviderDetails and
ProviderDetailsHistory tables outside of the session, runs the test,
and then clears the table and puts those old values in
this means that the tests have been cleaned up so that they do not
do operations twice in reverse. they've also been cleaned up
generally, including fixture optimisations and such
* tests on API endpoints that we do not explicitly sort should
either sort the results or compare results in an orderless way
(e.g. converting to a set)
* tests that touch the provider_details should reset values after
running, since the provider_details table is not torn down and
re-created between tests (unlike most tables)
