lark - Implement a Postgresql health check

Related to #issuenumber

Local Checklist

• Read our Contributing guide (for newcomers)
• Tests written and passing locally?
• Code style checked?
• QA-ed locally?
• Rebased with master branch?
• Configuration updated (if needed)?
• Documentation updated (if needed)?

What does this Merge Request do?

Adds a health check for an active database connection.

Why are we doing this? Any context of related work or Epic?

References #189 (closed)

Where should a reviewer start?

Start by reviewing lark/config/initializers/healthchecks.rb

Manual testing steps?

For healthy check in docker container

curl -v http://localhost:5000/health/complete

For local server that uses MEMORY for INDEX_ADAPTER & EVENT_ADAPTER

curl -v http://localhost:9292/health/complete

Database changes

New ENV variables

Screenshots

OK Postgres healthy check

not healthy check

Not OK Postgres Health check

Closes #189 (closed)