`postgresql.auth.password` defaulting to null causes errors in some cases on helm 3.17.1

[techno-tanoC]

Hello,

The default value of postgresql.auth.password in values.yaml is set to null, which can lead to errors in certain situations.

Error: values don't meet the specifications of the schema(s) in the following chart(s):
postgresql:
- postgresqlPassword: Invalid type. Expected: string, given: null

The postgresql.auth.password field is unnecessary when postgresql.existingSecret is specified, but it is still required.

https://github.com/getredash/contrib-helm-chart/blob/8b08dab164d9426d847df394e932fd902f01439b/charts/redash/values.yaml#L595-L596

This issue arises due to changes introduced in Helm 3.17.1 ( https://github.com/helm/helm/pull/12879 ).

Please consider setting a default string for postgresql.auth.password to prevent such errors.