Add a Pulsar IO MongoDB

[bbonnin]

Motivation

Provides a builtin MongoDB Connector, in order to ease the storage of JSON formated message in MongoDB. It's a sink connector.

Modifications

Add a new sub-module in the pulsar-iomodule.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• deploy the connector with configuration file containing the following fields:

configs:
  mongoUri: mongodb://hostname:port
  database: pulsar
  collection: messages

• start a mongodb instance
• send messages in the topic declared when deploying the connector
• check in MongoDB if the messages have been stored in the collection messages

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no
• The rest endpoints: no
• The admin cli options: no
• Anything that affects deployment: no

Documentation

• Does this pull request introduce a new feature? yes
  • a new sink connector for storing messages in MongoDB
• If yes, how is the feature documented? not documented
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[sijie]

@bbonnin great contribution! thank you

[bbonnin]

@sijie thank you for merging my first PR :) !!