Added Locking Mechanism to Reminders Handler

[b-quachtran]

Proposed changes:

• Added lock_store as an input to MessageProcessor so that handle_reminder can properly lock the conversation
• Updated handle_reminder to lock the conversation before retrieving the tracker store & executing
• Updated default_processor to pass in InMemoryLockStore as a param for test cases
• Resolves Issue Reminder Events Don't Acquire a Conversation Lock #7887

Status (please check what you already did):

• added some tests for the functionality
• updated the documentation
• updated the changelog (please check changelog for instructions)
• reformat files using black (please check Readme for instructions)

[b-quachtran]

@wochinge I added lock_store as an input parameter to MessageProcessor so that handle_reminder could lock the conversation, but not entirely sure if this is the best way to do it. Wdyt?

[wochinge]

Thanks for providing the fix! Will you also implement that for 2.x?

[b-quachtran]

@wochinge Yes, definitely. I'll create a PR for 2.X as well once this fix is good to go

[wochinge]

did you also test this manually? If so, how?

[b-quachtran]

@wochinge Yes, I tested manually using the ReminderBot with redis-server running locally and the SocketIO channel. Redis logs showed the lock correctly being acquired and deleted when the reminder was handled.

[wochinge]

Nice job 💯