Operations related to 'chats'.  A 'chat' may contain 2 or more participants
from 1 or 2 pods, and are different to rooms in that their membership is fixed
at creation time.

Operations related to connections to a Symphony pod.

Operations related to MessageMLv2 messages, which combine one or more of:

 1. a human-readable message (formatted using a subset of HTML called 'PresentationML')
 2. a machine readable JSON blob called the 'entity data'
 3. an attachment

See:

 * https://rest-api.symphony.com/docs/messagemlv2 for details on PresentationML's formatting capabilities
 * https://rest-api.symphony.com/docs/objects for details on MessageMLv2's entity data capabilities

Operations related to 'rooms'.  A 'room' is a named chat containing 1 or more
participants from 1 or 2 pods.

Operations related to 'streams'.  A 'stream' is the generic term for any kind
of message channel in the Symphony platform, and comes in one of several
flavours:

1. 1:1 chat
2. M:M chat
3. room
4. wall post

The primary difference between chats and rooms is that rooms have dynamic
membership whereas the membership of a chat is fixed at creation time.

In addition, each type of stream can be 'internal' (intra-pod) or 'external'
(include users from at most 1 other pod, aka 'cross-pod').

Operations related to users.  A user can be either a human or a service
account (bot).  Users can be identified in 3 separate ways:

1. via a user id - a Long that is globally unique across all pods
2. via an email address - a String, though only unique within a pod
3. via a username - a String, though only unique within a pod

Operations related to user connections and requests for those connections.
In Symphony, a user connection is an explicitly established relationship
between users in different pods.