Optional ExperimentalacceptOptionalinviteIf the caller has a keypair 3pid invite, the signing URL is passed in this parameter.
OptionalviaThe server names to try and join through in addition to those that are automatically chosen. Only the first 3 are actually used in the request, to avoid HTTP 414 Request-URI Too Long responses.
When accepting an invite, whether to accept encrypted history shared by the inviter via the experimental support for MSC4268.