fix: throw 500 error when redis goes down

[dracarys18]

Type of Change

• [x] Enhancement

Description

Created a global flag to check if redis is available or not if it's not available send 500 error to all reamaining requests.

Motivation and Context

Currently if redis goes down currently after reconnect_attempts reached fred will currently close the client and block the whole application.

How did you test it?

Manual

Checklist

• [x] I formatted the code cargo +nightly fmt --all
• [x] I addressed lints thrown by cargo clippy
• [x] I reviewed submitted code