Resolve "Non-PKCE OIDC clients broken"

Closes #744 (closed)

Does not require a changelog update because the original change causing this issue was not released.

aleksis/core/settings.py

@@ -375,6 +375,7 @@ OAUTH2_PROVIDER = {
     "OAUTH2_VALIDATOR_CLASS": "aleksis.core.util.auth_helpers.CustomOAuth2Validator",
     "OIDC_ENABLED": True,
     "REFRESH_TOKEN_EXPIRE_SECONDS": _settings.get("oauth2.token_expiry", 86400),
+    "PKCE_REQUIRED": False,
 }
 OAUTH2_PROVIDER_APPLICATION_MODEL = "core.OAuthApplication"
 OAUTH2_PROVIDER_GRANT_MODEL = "core.OAuthGrant"