Role: The role which is assigned to the client buyer. Each role implies a set of permissions granted to the client. Must be one of `CLIENT_DEAL_VIEWER`, `CLIENT_DEAL_NEGOTIATOR`, or `CLIENT_DEAL_APPROVER`.
"CLIENT_ROLE_UNSPECIFIED" - A placeholder for an undefined client
"CLIENT_DEAL_VIEWER" - Users associated with this client can see
publisher deal offers in the Marketplace. They can neither negotiate proposals nor approve deals. If this client is visible to publishers, they can send deal proposals to this client.
"CLIENT_DEAL_NEGOTIATOR" - Users associated with this client can
respond to deal proposals sent to them by publishers. They can also initiate deal proposals of their own.
"CLIENT_DEAL_APPROVER" - Users associated with this client can
approve eligible deals on your behalf. Some deals may still explicitly require publisher finalization. If this role is not selected, the sponsor buyer will need to manually approve each of their deals.