Make blinding enabled by default

Users can explicitly disable it, if desired, by setting the (hidden)
`[users] require_blind_keys = false` setting, but as of the upcoming
release that is now considered deprecated.

Author: jagerman

conftest.py

@@ -3,6 +3,7 @@
 from sogs import config
 
 config.DB_URL = 'defer-init'
+config.REQUIRE_BLIND_KEYS = False
 
 from sogs import web  # noqa: E402
 from sogs.model.room import Room  # noqa: E402

sogs/config.py

@@ -35,7 +35,7 @@
 ALPHABET_FILTERS = set()
 ALPHABET_SILENT = True
 FILTER_MODS = False
-REQUIRE_BLIND_KEYS = False
+REQUIRE_BLIND_KEYS = True
 TEMPLATE_PATH = 'templates'
 STATIC_PATH = 'static'
 UPLOAD_PATH = 'uploads'