fix: add more context to readiness check

[mutambaraf]

Description

This PR upgrades the /readiness health check to provide dependency information and also improve how we send back HTTP status codes.

Motivation and Context

How Has This Been Tested

Manual

{
    "application": {
        "status": "UP",
        "database": {
            "status": "UP",
            "message": "Connected"
        }
    }
}

Fixes

Changes

• 200 OK: Application is running and all critical dependencies (database) are available.
• 503 Service Unavailable: Application is running, but the database connection check failed.
• 500 Internal Server Error : Application is having internal errors, not able to check database connection .

Depends on

Tests included/Docs Updated?

• I have added tests to cover my changes.
• All relevant doc has been updated

[yoganandaness]

Do we want to have then, catch, if we are going to use await?

[yoganandaness]

@mutambaraf I noticed that, we are querying settings table for health check. Could we change it to select 1 to keep it light weight

user-office-core/apps/backend/src/datasources/postgres/SystemDataSource.ts

Line 10 in 909dae0

.raw('select * FROM "settings" LIMIT 1')

[yoganandaness]

Looks great @mutambaraf