Resolve "[OAuth] .well-known must be mounted under /"

Closes #606 (closed)

❯ curl localhost:8000/.well-known/openid-configuration
{"issuer": "http://localhost:8000", "authorization_endpoint": "http://localhost:8000/authorize/", "token_endpoint": "http://localhost:8000/token/", "userinfo_endpoint": "http://localhost:8000/userinfo/", "jwks_uri": "http://localhost:8000/.well-known/jwks.json", "response_types_supported": ["code", "token", "id_token", "id_token token", "code token", "code id_token", "code id_token token"], "subject_types_supported": ["public"], "id_token_signing_alg_values_supported": ["HS256"], "token_endpoint_auth_methods_supported": ["client_secret_post", "client_secret_basic"], "claims_supported": ["sub"]}%