fix: pass redis SSL config to connection pool

[tarvip]

What this PR does

This fix will pass SSL config properly to redis connection pool.
django-redis passes CONNECTION_POOL_KWARGS and not CONNECTION_POOL_CLASS_KWARGS to connection pool class, related django-redis code can be seen here.

Also, without this fix other settings max_connections and timeout are also not passed to connection pool.

I had issues with external Redis with in-transit encryption enabled using self-signed certs (Google managed Redis).
After changing this I can properly pass self-signed CA cert to redis client using REDIS_SSL_CA_CERTS env variable.

Which issue(s) this PR closes

There is no issue created for this problem.

Checklist

• Unit, integration, and e2e (if applicable) tests updated
• Documentation added (or pr:no public docs PR label added if not required)
• Added the relevant release notes label (see labels prefixed w/ release:). These labels dictate how your PR will
  show up in the autogenerated release notes.

[CLAassistant]

All committers have signed the CLA.

[JNKielmann]

We are running into the same problem trying to use oncall with a Redis on GCP with in-transit encryption enabled.

[tarvip]

We are running into the same problem trying to use oncall with a Redis on GCP with in-transit encryption enabled.

We have Grafana OnCall deployed using a Helm chart. As a workaround, I added the following env variable:

env:
  - name: REDIS_URI
    value: "$(REDIS_PROTOCOL)://$(REDIS_USERNAME):$(REDIS_PASSWORD)@$(REDIS_HOST):$(REDIS_PORT)/$(REDIS_DATABASE)?ssl_ca_certs=/mnt/redis-tls/server_ca.pem"

Redis CA cert is mounted to /mnt/redis-tls/server_ca.pem.

It would be nice to get this merged. Created this PR almost a month ago, no feedback so far.