dont let user update prov details version, and refactor tests

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/app/conftest.py

@@ -1,6 +1,7 @@
 import uuid
 from datetime import (datetime, date, timedelta)
 
+from sqlalchemy.orm.session import make_transient
 import requests_mock
 import pytest
 from flask import current_app
@@ -18,6 +19,8 @@ from app.models import (
     Permission,
     ProviderStatistics,
     ProviderDetails,
+    ProviderDetailsHistory,
+    ProviderRates,
     NotificationStatistics,
     ServiceWhitelist,
     KEY_TYPE_NORMAL, KEY_TYPE_TEST, KEY_TYPE_TEAM,
@@ -857,3 +860,33 @@ def sample_provider_rate(notify_db, notify_db_session, valid_from=None, rate=Non
         valid_from=valid_from if valid_from is not None else datetime.utcnow(),
         rate=rate if rate is not None else 1,
     )
+
+
+@pytest.fixture
+def restore_provider_details(notify_db, notify_db_session):
+    """
+    We view ProviderDetails as a static in notify_db_session, since we don't modify it... except we do, we updated
+    priority. This fixture is designed to be used in tests that will knowingly touch provider details, to restore them
+    to previous state.
+
+    Note: This doesn't technically require notify_db_session (only notify_db), but kept as a requirement to encourage
+    good usage - if you're modifying ProviderDetails' state then it's good to clear down the rest of the DB too
+    """
+    existing_provider_details = ProviderDetails.query.all()
+    existing_provider_details_history = ProviderDetailsHistory.query.all()
+    # make transient removes the objects from the session - since we'll want to delete them later
+    for epd in existing_provider_details:
+        make_transient(epd)
+    for epdh in existing_provider_details_history:
+        make_transient(epdh)
+
+    yield
+
+    # also delete these as they depend on provider_details
+    ProviderRates.query.delete()
+    ProviderDetails.query.delete()
+    ProviderDetailsHistory.query.delete()
+    notify_db.session.commit()
+    notify_db.session.add_all(existing_provider_details)
+    notify_db.session.add_all(existing_provider_details_history)
+    notify_db.session.commit()