The `delay_id` is generated by the server. It SHOULD contain only valid non-surrogate Unicode codepoints except `:` and `NUL`, and MUST NOT exceed 255 bytes.
The `delay_id` is an [opaque identifier](https://spec.matrix.org/v1.16/appendices/#opaque-identifiers) generated by the server.
The server MAY round the delay up to a maximum of 30 seconds away from the request.