Call a Matrix client API.

This is a lower-level function; generally, clients will want to call one of the higher-level functions from Polyjuice.Client.

Get the child spec for the sync process.

listener will receive messages with the sync results. Messages include:

• {:connected}: the process has connected to the homeserver
• {:disconnected}: the process has been disconnected from the homeserver
• {:initial_sync_completed}: the first sync has completed
• {:limited, room_id, prev_batch}: a room's timeline has been limited. Previous messages can be fetched using the prev_batch
• {:message, room_id, event}: a message event has been received
• {:state, room_id, event}: a state event has been received
• {:invite, room_id, inviter, invite_state}: the user was invited to a room
• {:left, room_id}: the user left a room

opts is a keyword list of options:

• filter: (string or map) the filter to use with the sync

Generate a unique transaction ID.