refactor: App.hs and related changes (#1725)

* Use ExceptT to avoid 'staircasing' case analysis in App.hs
* Split large function in App.hs into individual handler functions
* Adapt API of Auth.hs, OpenApi.hs etc. to simplify the use of those modules in App.hs
* Split optional rollback functionality into Middleware
* Unify SimpleError and ApiRequestError into one Error type, so it can be used across modules

test/io-tests/test_io.py

@@ -297,6 +297,7 @@ def test_expected_config_from_db_settings(defaultenv, role, expectedconfig):
 
     assert dumpconfig(configpath=config, env=env) == expected
 
+
 @pytest.mark.parametrize(
     "config",
     [conf for conf in CONFIGSDIR.iterdir() if conf.suffix == ".config"],
@@ -604,6 +605,7 @@ def test_max_rows_notify_reload(defaultenv):
         # reset max-rows config on the db
         postgrest.session.post("/rpc/reset_max_rows_config")
 
+
 def test_invalid_role_claim_key_notify_reload(defaultenv):
     "NOTIFY reload config should show an error if role-claim-key is invalid"