Integrate mod-source-record-storage with mod-pubsub

Motivation

To provide the mod-record-storage with the ability to send and receive events using mod-pubsub.

Steps

• add mod-pubsub-client dependency
• determine the types of events that the SRS publishes and receives (use event type matrix)
• create MessagingDescriptor.json
• add module registration in pub-sub on enabling the module for a tenant
• add stub implementation of endpoints to receive events that module is subscribed

Results

mod-record-storage can publish events to mod-pubsub and receive events that it is subscribed