[CHE-120] Add Total Posts Display On Threads

[howardsun-dev]

Description

This PR aims to:

• add total post count on individual threads
• add total reply count per thread on threadDisplay for All
• add total reply count per thread on threadDisplay custom forums

Extra:

• add to queryHelper in server/controllers/helpers/queryHelpers.ts to handle MongoDb aggregate for sorting
• add type to forums for postCount

Jira Task

CHE-120

Testing Instructions

• Ensure branches are up to date.
• Navigate to Forums and click through All Forums and each Forum (ex: General) to see if reply count appears on the screen for each individual thread.
• Click into the individual threads, and there should be a total post count for that thread (including the OP)

Checklist

All Team Members

• I added a descriptive title to this PR.
• I filled out the Description, Jira Task, and Testing Instructions sections above.
• I added or updated [Jest unit tests]for any changes to components, server-side controllers, etc.
• I ran npm run docker-test in my local environment to check that this PR passes all unit tests.
• I did a quick check to make sure my code changes follow the recomended style guide.

Additional Notes, Images, etc.

(This is space for any additional information or attachments you'd like to add as part of this PR.)

[seantokuzo]

Left a few comments but this all is working great! Nice work Howard!