Add support for thread activities, could be pre-defined for use-cases.

[sanchitrk]

Create thread activities as part of timeline entries, helps the team log events on what is happening with the threads.

For example, if the thread is created by the customer, create activity like

• The customer reached out via chat/email

If the stage/status was updated like from waiting on the customer

• the Status changed to waiting on a customer, etc,

When a label is added

• Label added by you.

[sanchitrk]

this is de-prioritized for now, after events.