Rasa Chart currently requires Bitnami Charts that are no longer available

[laberning]

Currently the Rasa Chart uses the following dependencies

Repository	Name	Version
https://charts.bitnami.com/bitnami	postgresql	~10.16.2
https://charts.bitnami.com/bitnami	rabbitmq	~8.32.2
https://charts.bitnami.com/bitnami	redis	~15.7.6

All those are no longer available, so a helm dependency update fails with unmatchable requirements.

Updating the Charts to the versions below works, but requires tweaking the postgresql configuration a bit, since the name and defaults for keys in the secrets have changed with the new bitnami charts:

postgresql:
  ...
  # used to be "postgresql-password" in older versions of the bitnami charts
  existingSecretKey: postgres-password
  auth:
    username: "postgres"
    database: "rasa"

Repository	Name	Version
https://charts.bitnami.com/bitnami	postgresql	~12.2.1
https://charts.bitnami.com/bitnami	rabbitmq	~11.10.0
https://charts.bitnami.com/bitnami	redis	~17.8.0