Software implementing this work-in-progress specification MUST NOT use the unprefixed `extended-invite` capability name. Instead, implementations SHOULD use the `draft/extended-invite` capability name to be interoperable with other software implementing a compatible work-in-progress version.
This specification extends the `INVITE` command to allow for an optional reason. The reason can be used to give more context around why the invite was sent.
Servers implementing this spec MUST also implement the `invite-notify` capability. Clients SHOULD negotiate the `invite-notify` capability when negotiating `extended-invite`.
Clients that have negotiated the `extended-invite` capability MAY add a final parameter on an `/INVITE` command. This parameter is to give the target user context for the invite. This parameter MUST NOT cause the message to exceed the maximum allowable line length of the server.
Servers that implement `extended-invite` MUST accept `INVITE` commands with three parameters. If the user receiving the invite has negotiated `extended-invite`, the server sends the final parameter to that user. Additionally, the final parameter is added to the `INVITE` command sent to any users that have negotiated both the `extended-invite` and `invite-notify` capabilities.