Redis unavailability raises uncatched error in backend and makes backend unavailable

[rhanka]

when redis is down the following error appears in log :
Error: connect ETIMEDOUT at Socket.<anonymous> (/deces-backend/node_modules/ioredis/built/Redis.js:170:41) at Object.onceWrapper (node:events:627:28) at Socket.emit (node:events:513:28) at Socket._onTimeout (node:net:580:8) at listOnTimeout (node:internal/timers:573:17) at process.processTimers (node:internal/timers:514:7) { errorno: 'ETIMEDOUT', code: 'ETIMEDOUT', syscall: 'connect' }
It should be catched and timestamped as a json log of the backend

Moreover, when this happen, the backend can't handle even a simple search request. This is a bug, redis should only block the bulk api.